Add Accordion web part implementation with dynamic SharePoint list integration

- Created Accordion web part with SPFx 1.4.1 framework.
- Implemented dynamic loading of SharePoint lists and fields.
- Added configuration options for title, content, and category fields.
- Included support for multiple open sections and initial state settings.
- Developed HTML sanitizer for rich text content.
- Implemented accessible accordion UI with category grouping.
- Added localization support for English and German languages.
- Created necessary configuration files for deployment and asset management.
- Added validation script to ensure project compliance with standards.

.gitignore

@@ -0,0 +1,19 @@
+node_modules/
+lib/
+dist/
+temp/
+release/
+solution/
+sharepoint/solution/
+*.sppkg
+*.tgz
+coverage/
+*.resx.ts
+*.scss.ts
+*.log
+npm-debug.log*
+.vs/
+.idea/
+.DS_Store
+Thumbs.db
+