Add Expiry Indicator functionality with configuration and command set

- Implemented ExpiryItemService to manage expiry date logic for list items.
- Created ExpiryModels to define types and structures for expiry configurations and rules.
- Added RestError utility for handling API response errors.
- Developed ExpiryIndicatorFieldCustomizer to display expiry information in list views.
- Introduced ExpiryIndicatorCommandSet for extending expiry dates and managing settings.
- Added settings dialog for configuring expiry settings.
- Implemented localization support for English and German languages.
- Added TypeScript configuration files for project setup.
- Included TSLint configuration for code quality enforcement.

src/extensions/expiryIndicatorCommandSet/ExpiryIndicatorCommandSet.manifest.json

@@ -0,0 +1,26 @@
+{
+  "$schema": "https://developer.microsoft.com/json-schemas/spfx/client-side-extension-manifest.schema.json",
+  "id": "cd58f5d9-ffc8-4df7-a910-3054842d7abf",
+  "alias": "ExpiryIndicatorCommandSet",
+  "componentType": "Extension",
+  "extensionType": "ListViewCommandSet",
+  "version": "1.0.0",
+  "manifestVersion": 2,
+  "items": {
+    "EXTEND_ONE_YEAR": {
+      "title": {
+        "default": "Extend expiry +1 year",
+        "de-de": "Ablaufdatum +1 Jahr"
+      },
+      "type": "command"
+    },
+    "SETTINGS": {
+      "title": {
+        "default": "Expiry settings",
+        "de-de": "Expiry-Einstellungen"
+      },
+      "type": "command"
+    }
+  }
+}
+