Add Portal Settings Web Part with styles, localization, and tests

- Implemented the PortalSettings Web Part with a new manifest and TypeScript file.
- Created SCSS styles for the Web Part, defining various UI elements and responsive design.
- Added localization support for English and German languages.
- Developed tests for Provider Registry and static assets validation.
- Included PowerShell script for project validation.

config/serve.json

@@ -4,13 +4,7 @@
   "https": true,
   "serveConfigurations": {
     "default": {
-      "pageUrl": "http://clshp001/SitePages/PortalSettings.aspx",
-      "customActions": {
-        "cd6b9e8d-07b9-4468-b230-6bb35acd9a5f": {
-          "location": "ClientSideExtension.ApplicationCustomizer",
-          "properties": {}
-        }
-      }
+      "pageUrl": "http://clshp001/_layouts/15/workbench.aspx"
     }
   }
 }