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.

src/webparts/portalSettings/loc/de-de.js

@@ -0,0 +1,7 @@
+define([], function() {
+  return {
+    "PropertyPaneDescription": "Portal-Einstellungen",
+    "BasicGroupName": "Allgemein",
+    "TitleFieldLabel": "Titel"
+  };
+});

src/webparts/portalSettings/loc/en-us.js

@@ -0,0 +1,7 @@
+define([], function() {
+  return {
+    "PropertyPaneDescription": "Portal Settings",
+    "BasicGroupName": "General",
+    "TitleFieldLabel": "Title"
+  };
+});

src/webparts/portalSettings/loc/myStrings.d.ts

@@ -0,0 +1,10 @@
+declare interface IPortalSettingsWebPartStrings {
+  PropertyPaneDescription: string;
+  BasicGroupName: string;
+  TitleFieldLabel: string;
+}
+
+declare module 'PortalSettingsWebPartStrings' {
+  const strings: IPortalSettingsWebPartStrings;
+  export = strings;
+}