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.

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

@@ -0,0 +1,31 @@
+declare interface IAccordionWebPartStrings {
+  PropertyPaneDescription: string;
+  DataGroupName: string;
+  BehaviorGroupName: string;
+  ListFieldLabel: string;
+  TitleFieldLabel: string;
+  ContentFieldLabel: string;
+  CategoryFieldLabel: string;
+  SortFieldLabel: string;
+  SortAscendingLabel: string;
+  AllowMultipleLabel: string;
+  InitialStateFieldLabel: string;
+  InitialCollapsed: string;
+  InitialFirst: string;
+  InitialAll: string;
+  ShowCategoriesLabel: string;
+  SelectOption: string;
+  NoCategoryOption: string;
+  ConfigureMessage: string;
+  LoadingMessage: string;
+  EmptyMessage: string;
+  LoadErrorMessage: string;
+  ExpandLabel: string;
+  CollapseLabel: string;
+  DefaultCategory: string;
+}
+
+declare module 'AccordionWebPartStrings' {
+  const strings: IAccordionWebPartStrings;
+  export = strings;
+}