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.

config/config.json

@@ -0,0 +1,28 @@
+{
+  "$schema": "https://developer.microsoft.com/json-schemas/spfx-build/config.2.0.schema.json",
+  "version": "2.0",
+  "bundles": {
+    "expiry-indicator-field-customizer": {
+      "components": [
+        {
+          "entrypoint": "./lib/extensions/expiryIndicator/ExpiryIndicatorFieldCustomizer.js",
+          "manifest": "./src/extensions/expiryIndicator/ExpiryIndicatorFieldCustomizer.manifest.json"
+        }
+      ]
+    },
+    "expiry-indicator-command-set": {
+      "components": [
+        {
+          "entrypoint": "./lib/extensions/expiryIndicatorCommandSet/ExpiryIndicatorCommandSet.js",
+          "manifest": "./src/extensions/expiryIndicatorCommandSet/ExpiryIndicatorCommandSet.manifest.json"
+        }
+      ]
+    }
+  },
+  "externals": {},
+  "localizedResources": {
+    "ExpiryIndicatorStrings": "lib/extensions/expiryIndicator/loc/{locale}.js",
+    "ExpiryIndicatorCommandSetStrings": "lib/extensions/expiryIndicatorCommandSet/loc/{locale}.js"
+  }
+}
+