feat(notimplemented): Update error messages to include a link for not implemented APIs

Author: jeromelaban

doc/articles/uno-notimplemented-types.md

@@ -0,0 +1,14 @@
+## The member/type is not implemented
+
+Uno Platform is built around providing the full APIs provided by WinRT and WinUI, by replicating the available surface to be used in Uno Platform apps.
+
+This surface is very large and with the help of the community, the Uno Platform team is hard at work to add support for APIs that are marked as "Not Implemented".
+
+If you're visiting this page after having clicked on a link in your application's debug log or exception view, this means you're using directly or indirectly an API that is not implemented.
+
+Multiple directions are available:
+- Make sure that you are using the latest available stable packages for Uno Platform (Uno.WinUI or Uno.UI)
+- Find the API (Type, method or property) in the Issues list, and if it's not already present, create one so the team knows you're trying to use it. Make sure to let us know your use case and it may drive priorities.
+- If you're up for it, you can contribute an implementation for this API
+
+The Uno Platform team [offers professional support](https://platform.uno/support/) to get issues sorted our faster.

src/Uno.Foundation/Metadata/ApiInformation.cs

@@ -143,7 +143,7 @@ public static bool IsEnumNamedValuePresent(string enumTypeName, string valueName
 
 		internal static void TryRaiseNotImplemented(string type, string memberName)
 		{
-			var message = $"The member {memberName} is not implemented in Uno.";
+			var message = $"The member {memberName} is not implemented in Uno. For more information visit https://aka.platform.uno/notimplemented?m={Uri.EscapeDataString(type + "." + memberName)}";
 
 			if (IsFailWhenNotImplemented)
 			{

src/Uno.UWPSyncGenerator/Generator.cs

@@ -984,7 +984,7 @@ private void BuildNotImplementedException(IndentedStringBuilder b, ISymbol membe
 			if (forceRaise)
 			{
 				b.AppendLineInvariant(
-					$"throw new global::System.NotImplementedException(\"The member {memberName} is not implemented in Uno.\");"
+					$"throw new global::System.NotImplementedException(\"The member {memberName} is not implemented. For more information visit https://aka.platform.uno/notimplemented?m={Uri.EscapeDataString(memberName)}\");"
 				);
 			}
 			else