Add Current Navigation Application Customizer

- Created a new SPFx Application Customizer for current navigation.
- Implemented core functionality to fetch and render navigation items from a SharePoint term set.
- Added styles for the navigation component using SCSS.
- Included localization support for English and German languages.
- Developed unit tests for core navigation functionalities.
- Configured TypeScript and TSLint settings for the project.
- Added validation scripts for static assets and package configuration.

config/config.json

@@ -0,0 +1,16 @@
+{
+  "$schema": "https://developer.microsoft.com/json-schemas/spfx-build/config.2.0.schema.json",
+  "version": "2.0",
+  "bundles": {
+    "current-navigation-application-customizer": {
+      "components": [{
+        "entrypoint": "./lib/extensions/currentNavigation/CurrentNavigationApplicationCustomizer.js",
+        "manifest": "./src/extensions/currentNavigation/CurrentNavigationApplicationCustomizer.manifest.json"
+      }]
+    }
+  },
+  "externals": {},
+  "localizedResources": {
+    "CurrentNavigationApplicationCustomizerStrings": "lib/extensions/currentNavigation/loc/{locale}.js"
+  }
+}