TOC refresh for supported platforms

- change TOC to create new section to answer "where is SPFx supported"
- rename & move viva connections & msteams => parallel to SPFx node in TOC
- move sps on-prem support pages => under new section
- introduce new spo support page => under new section

Author: andrewconnell

docs/spfx/spfx-sharepoint-online.md

@@ -0,0 +1,17 @@
+---
+title: SharePoint Framework support on SharePoint Online
+description: SharePoint Online always has the broadest and most up-to-date support for the SHarePoint Framework (SPFx). The SharePoint Framework is also the recommended customization and extensibility development model for SharePoint Online.
+ms.date: 09/08/2021
+ms.prod: sharepoint
+localization_priority: Priority
+---
+
+# SharePoint Framework support on SharePoint Online
+
+SharePoint Online always has the broadest and most up-to-date support for the SHarePoint Framework (SPFx). The SharePoint Framework is also the recommended customization and extensibility development model for SharePoint Online.
+
+All published versions of SFPx, as well as the latest betas, are published and available on SharePoint Online. This means that regardless of the version you use to build custom SPFx components, they'll always work on SharePoint Online sites.
+
+Each SPFx component's manifest tells the SPFx runtime on SharePoint pages what package dependencies, including the specific versions, each component depends on. The SPFx runtime uses this information to ensure the correct SPFx libraries are loaded on the page prior to loading initializing your SPFx components.
+
+Unless otherwise stated, all capabilities of SPFx are supported in SharePoint Online.

docs/spfx/supported-extensibility-platforms-overview.md

@@ -0,0 +1,46 @@
+---
+title: Supported extensibility platforms - overview
+description: Learn what platforms support customizations and rely on the SharePoint Framework for their extensibility opportunities available to developers.
+ms.date: 09/08/2021
+ms.prod: sharepoint
+localization_priority: Priority
+---
+
+# Supported extensibility platforms - overview
+
+In this section, learn what platforms support customizations and rely on the SharePoint Framework (SPFx) for their extensibility opportunities available to developers. Some platforms are completely reliant on the SPFx for their customization & extensibility story, while others support it as one of multiple options.
+
+## SharePoint Online
+
+SharePoint Online always has the broadest and most up-to-date support for the SPFx. The SPFx is also the recommended customization and extensibility development model for SharePoint Online.
+
+Learn more about using SPFx on SharePoint Online: [SPFx support for SharePoint Online](spfx-sharepoint-online.md).
+
+## SharePoint Server SE
+
+> [!IMPORTANT]
+> SharePoint Server Subscription Edition (SE), announced as a preview in July 2021, supports the same SPFx versions as SharePoint Server 2019.
+
+## SharePoint Server 2019
+
+SharePoint Server 2019 includes support for the SPFx up to version v1.4.1.
+
+Learn more about using SPFx on SharePoint Server 2019: [SPFx support for SharePoint Server 2019](sharepoint-2019-support.md).
+
+## SharePoint Server 2016
+
+SharePoint Server 2016 includes support for the SPFx up to version v1.1.0. The support for the SPFx on SharePoint Server 2016 was introduced in Feature Pack 2.
+
+Learn more about using SPFx on SharePoint Server 2016: [SPFx support for SharePoint Server 2016](sharepoint-2016-support.md).
+
+## Microsoft Teams
+
+Microsoft Teams offers developers multiple options to create custom apps and extensibility. Developers can use the SPFx to create and deploy custom apps for Microsoft Teams.
+
+Learn more about using SPFx for Microsoft Teams: [SPFx support for Microsoft Teams](build-for-teams-overview.md).
+
+## Microsoft Viva Connections
+
+Microsoft Viva Connections, your gateway to modern engagement experiences is designed to keep everyone in your organization engaged and informed. Viva Connections entirely relies on SharePoint for it's customization and extensibility story. This includes both the Viva Connections desktop and mobile experiences. Both of these experiences rely on the SPFx for all customizations.
+
+Learn more about using SPFx on Viva Connections: [SPFx support for Viva Connections](viva/overview-viva-connections.md).

docs/toc.yml

@@ -235,20 +235,6 @@
       href: spfx/library-component-overview.md
     - name: Library component tutorial
       href: spfx/library-component-tutorial.md
-  - name: Viva Connections extensibility
-    items:
-    - name: Overview
-      href: spfx/viva/overview-viva-connections.md
-    - name: Tutorials
-      items:
-      - name: Build your first SharePoint Adaptive Card Extension
-        href: spfx/viva/get-started/build-first-sharepoint-adaptive-card-extension.md
-      - name: Advanced Card View Functionality
-        href: spfx/viva/get-started/advanced-card-view-functionality.md
-      - name: Advanced Quick View Functionality
-        href: spfx/viva/get-started/advanced-quick-view-functionality.md
-      - name: Adaptive Card Extensions and Teams Apps
-        href: spfx/viva/get-started/adaptive-card-extensions-and-teams.md
   - name: Publish to marketplace
     items:
     - name: Overview
@@ -351,10 +337,6 @@
       href: spfx/tenant-scoped-deployment.md
     - name: Optimize builds for production
       href: spfx/toolchain/optimize-builds-for-production.md
-    - name: SharePoint 2016 support
-      href: spfx/sharepoint-2016-support.md
-    - name: SharePoint 2019 support
-      href: spfx/sharepoint-2019-support.md
   - name: Concepts & scenarios
     items:
     - name: Localize web parts
@@ -440,6 +422,16 @@
       href: spfx/use-developer-dashboard.md
     - name: Maintenance mode for client-side web parts
       href: general-development/client-side-web-parts-maintenance-mode.md
+  - name: Supported extensibility platforms
+    items:
+    - name: Overview
+      href: spfx/supported-extensibility-platforms-overview.md
+    - name: SharePoint Online
+      href: spfx/spfx-sharepoint-online.md
+    - name: SharePoint 2019 support
+      href: spfx/sharepoint-2019-support.md
+    - name: SharePoint 2016 support
+      href: spfx/sharepoint-2016-support.md
   - name: Release notes & roadmap
     items:
     - name: Overview
@@ -480,7 +472,7 @@
       href: spfx/release-1.1.md
     - name: SPFx v1.0.0 - February 22, 2017
       href: spfx/release-1.0.0.md
-- name: Build for Microsoft Teams
+- name: Microsoft Teams
   items:
   - name: Overview
     href: spfx/build-for-teams-overview.md
@@ -496,6 +488,20 @@
     href: spfx/build-for-teams-meeting-app.md
   - name: Considerations
     href: spfx/build-for-teams-considerations.md
+- name: Microsoft Viva Connections
+  items:
+  - name: Overview
+    href: spfx/viva/overview-viva-connections.md
+  - name: Tutorials
+    items:
+    - name: Build your first SharePoint Adaptive Card Extension
+      href: spfx/viva/get-started/build-first-sharepoint-adaptive-card-extension.md
+    - name: Advanced Card View Functionality
+      href: spfx/viva/get-started/advanced-card-view-functionality.md
+    - name: Advanced Quick View Functionality
+      href: spfx/viva/get-started/advanced-quick-view-functionality.md
+    - name: Adaptive Card Extensions and Teams Apps
+      href: spfx/viva/get-started/adaptive-card-extensions-and-teams.md
 - name: Business Apps & Process Automation
   items:
   - name: Overview