Add endpoints: UpdateTenantTheme and ApplyTheme

Add documentation about 2 endpoints with sample code '/_api/thememanager/UpdateTenantTheme' and '/_api/thememanager/ApplyTheme'

Author: siata13

docs/declarative-customization/site-theming/sharepoint-site-theming-rest-api.md

@@ -25,12 +25,16 @@ The following REST commands are available for working with site themes:
 * __AddTenantTheme__ – create a new theme; similar to the Add-SPOTheme SharePoint cmdlet
 * __DeleteTenantTheme__ – remove a theme from the tenant store; similar to the Remove-SPOTheme PowerShell cmdlet
 * __GetTenantThemingOptions__ – read theme settings
+* __ApplyTheme__ – apply tenant theme to site
+* __UpdateTenantTheme__ – updates tenant theme definition
 
 The URL for theme management REST commands is based on _api/thememanager. For example, the following are the endpoints for the commands:
 
 * `http://<site url>/_api/thememanager/AddTenantTheme`
 * `http://<site url>/_api/thememanager/DeleteTenantTheme`
 * `http://<site url>/_api/thememanager/GetTenantThemingOptions`
+* `http://<site url>/_api/thememanager/ApplyTheme`
+* `http://<site url>/_api/thememanager/UpdateTenantTheme`
 
 ## AddTenantTheme
 
@@ -141,6 +145,111 @@ function RestRequest(url,params) {
 RestRequest("/_api/thememanager/GetTenantThemingOptions");
 ```
 
+## ApplyTheme
+
+The following JavaScript sample code shows how to apply theme to the site.
+
+```javascript
+function RestRequest(url,params) {
+  var req = new XMLHttpRequest();
+  req.onreadystatechange = function ()
+        {
+            if (req.readyState != 4) // Loaded
+                return;
+            console.log(req.responseText);
+        };
+  req.open("POST",url,true); 
+  req.setRequestHeader("Content-Type", "application/json;charset=utf-8");
+  req.setRequestHeader("ACCEPT", "application/json; odata.metadata=minimal");
+  req.setRequestHeader("x-requestdigest", _spPageContextInfo.formDigestValue);
+  req.setRequestHeader("ODATA-VERSION","4.0");
+  req.send(params ? JSON.stringify(params) : void 0);
+}
+var pal = {
+    "palette" : {
+        "themePrimary": "#1BF242",
+        "themeLighterAlt": "#0d0b00",
+        "themeLighter": "#0b35bc",
+        "themeLight": "#322d00",
+        "themeTertiary": "#6a5f00",
+       "themeSecondary": "#1B22F2",
+        "themeDarkAlt": "#ffe817",
+        "themeDark": "#ffed4b",
+        "themeDarker": "#fff171",
+        "neutralLighterAlt": "#252525",
+        "neutralLighter": "#282828",
+        "neutralLight": "#313131",
+        "neutralQuaternaryAlt": "#3f3f3f",
+        "neutralQuaternary": "#484848",
+        "neutralTertiaryAlt": "#4f4f4f",
+        "neutralTertiary": "#c8c8c8",
+        "neutralSecondaryAlt": "#d0d0d0",
+        "neutralSecondary": "#dadada",
+        "neutralPrimary": "#ffffff",
+        "neutralDark": "#eaeaea",
+        "black": "#f8f8f8",
+        "white": "#1f1f1f",
+        "primaryBackground": "#1f1f1f",
+        "primaryText": "#ffffff",
+        "error": "#ff5f5f"
+    }
+}
+RestRequest("/_api/thememanager/ApplyTheme", {name:"Sounders Rave Green", themeJson: JSON.stringify(pal)});
+```
+
+## UpdateTenantTheme
+
+The following JavaScript sample code shows how to update tenant theme.
+
+```javascript
+function RestRequest(url,params) {
+  var req = new XMLHttpRequest();
+  req.onreadystatechange = function ()
+        {
+            if (req.readyState != 4) // Loaded
+                return;
+            console.log(req.responseText);
+        };
+  req.open("POST",url,true); 
+  req.setRequestHeader("Content-Type", "application/json;charset=utf-8");
+  req.setRequestHeader("ACCEPT", "application/json; odata.metadata=minimal");
+  req.setRequestHeader("x-requestdigest", _spPageContextInfo.formDigestValue);
+  req.setRequestHeader("ODATA-VERSION","4.0");
+  req.send(params ? JSON.stringify(params) : void 0);
+}
+var pal = {
+    "palette" : {
+			"themePrimary": "#008cff",
+			"themeLighterAlt": "#f5faff",
+			"themeLighter": "#d6edff",
+			"themeLight": "#b3ddff",
+			"themeTertiary": "#66baff",
+			"themeSecondary": "#1f9aff",
+			"themeDarkAlt": "#007ee6",
+			"themeDark": "#006bc2",
+			"themeDarker": "#004f8f",
+			"neutralLighterAlt": "#f8f8f8",
+			"neutralLighter": "#f4f4f4",
+			"neutralLight": "#eaeaea",
+			"neutralQuaternaryAlt": "#dadada",
+			"neutralQuaternary": "#d0d0d0",
+			"neutralTertiaryAlt": "#c8c8c8",
+			"neutralTertiary": "#595959",
+			"neutralSecondary": "#373737",
+			"neutralPrimaryAlt": "#2f2f2f",
+			"neutralPrimary": "#000000",
+			"neutralDark": "#151515",
+			"black": "#0b0b0b",
+			"white": "#ffffff",
+			"primaryBackground": "#ffffff",
+			"primaryText": "#000000",
+			"disabledBackground": "#f4f4f4",
+			"disabledText": "#c8c8c8"
+    }
+}
+RestRequest("/_api/thememanager/UpdateTenantTheme", {name:"Sounders Rave Green", themeJson: JSON.stringify(pal)});
+```
+
 ## See also
 
 * [SharePoint site theming overview](sharepoint-site-theming-overview.md)