feat: Enhance MegaMenu with localization, caching, and new properties

- Added localization support for loading states, empty navigation, and submenu actions in both German and English.
- Introduced new properties in IMenuItem for description, openInNewWindow, and external links.
- Updated SPTermStorePickerService to handle cache versioning and language-specific caching.
- Implemented a new MegaMenuCore service for handling term properties, cache management, and navigation URL resolution.
- Refactored TaxonomyNavigationService to build menu hierarchy and filter hidden terms.
- Added automated tests for MegaMenu core functionalities and static asset validation.
- Removed unused ItemDictionary service.
- Created a comprehensive ToDo document outlining the implementation status and future tasks.

tests/tsconfig.json

@@ -0,0 +1,17 @@
+{
+  "compilerOptions": {
+    "target": "es5",
+    "module": "commonjs",
+    "moduleResolution": "node",
+    "outDir": "../temp/tests",
+    "rootDir": "..",
+    "skipLibCheck": true,
+    "types": [],
+    "lib": ["es5", "dom", "es2015.collection"]
+  },
+  "files": [
+    "../src/services/ISPTermStorePickerService.ts",
+    "../src/services/MegaMenuCore.ts",
+    "MegaMenuCore.test.ts"
+  ]
+}