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.

.gitignore

@@ -0,0 +1,8 @@
+node_modules/
+lib/
+temp/
+dist/
+sharepoint/solution/debug/
+sharepoint/solution/*.sppkg
+npm-debug.log*
+*.tsbuildinfo