Adding premilinary SP2019 dev platform supportability documentation

Author: VesaJuvonen

docs/general-development/sharepoint-2019-development-platform.md

@@ -0,0 +1,36 @@
+---
+title: SharePoint 2019 development platform
+ms.date: 07/12/2018
+ms.prod: sharepoint
+ms.assetid: e0602381-ae11-41be-6a7e-9e47e9f246d6
+---
+
+# SharePoint 2019 development platform
+
+This article contains preliminary details around supported development capabilities in the SharePoint 2019.
+
+> [!IMPORTANT] 
+> This list is still subject to change until actual official release of SharePoint 2019. This page will be updated accordingly when there are changes in the supportability statements.
+
+**Supported capabilities**
+
+* Modern and classic pages
+* Modern sites - modern team and communication site
+    * Classic sites are also supported
+* SharePoint Framework client-side web parts
+* SharePoint Framework extensions
+* Webhooks as in SharePoint Online
+* Asset packaging and automatic JavaScript file hosting from app catalog
+* Column formatting
+
+**Not supported capabilities**
+
+* Site Designs and Site Scripts
+* Hub sites
+* Site collection app catalog
+* "Tenant" properties
+
+Supported SharePoint Framework version for the SharePoint 2019 will be SharePoint Framework v1.4. SharePoint Framework Yeoman generator will be updated to have this option included in the version selection. 
+
+> [!NOTE] 
+> If you need to write SharePoint Framework components for SharePoint 2019 before Yeoman generator is updated, you can install SharePoint Framework 1.4 and use that as the generator for your SharePoint 2019 components. 

docs/general-development/what-s-new-for-developers-in-sharepoint.md

@@ -370,8 +370,8 @@
 - name: SharePoint development overview
   href: general-development/sharepoint-development-overview.md
   items:
-  - name: What's new for developers in SharePoint
-    href: general-development/what-s-new-for-developers-in-sharepoint.md  
+  - name: What's new for developers in SharePoint 2019
+    href: general-development/sharepoint-2019-development-platform.md  
   - name: SharePoint glossary
     href: general-development/sharepoint-glossary.md  
   - name: Protocol handler error in SharePoint 2016