Improve new docs site. (#2843)

* Improve parameter padding and add discord link.

* Update xref service for docs.

Reason: https://github.com/dotnet/docfx/issues/9659

* Update docs readme to specify docfx version.

* Update to latest DocFX.

* update action & add manual trigger

.github/workflows/docs.yml

@@ -4,6 +4,7 @@ on:
   push:
     tags:
       - '*'
+  workflow_dispatch:
       
 jobs:
   build:
@@ -18,7 +19,7 @@ jobs:
         dotnet-version: 8.0.x
 
     - name: Setup DocFX
-      run: dotnet tool install -g docfx --version 2.71.0
+      run: dotnet tool install -g docfx --version 2.75.2
 
     - name: Build DNet docs
       run: docfx docs/docfx.json