feat: Add comprehensive plugin API documentation and example plugin

- Introduced PLUGIN_API.md for detailed plugin development guidelines.
- Implemented PLUGIN_SYSTEM_IMPLEMENTATION.md summarizing all requested features.
- Created example-plugin showcasing all API features including commands, message interceptors, settings, and notifications.
- Added plugin-metadata.json for the example plugin with relevant metadata.

package-lock.json

@@ -1,14 +1,15 @@
 {
   "name": "paarrot",
-  "version": "4.11.26",
+  "version": "4.11.73",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "paarrot",
-      "version": "4.11.26",
+      "version": "4.11.73",
       "license": "AGPL-3.0-only",
       "dependencies": {
+        "adm-zip": "^0.5.16",
         "body-parser": "2.2.2",
         "cors": "2.8.6",
         "electron-squirrel-startup": "^1.0.1",
@@ -1668,6 +1669,15 @@
         "url": "https://opencollective.com/express"
       }
     },
+    "node_modules/adm-zip": {
+      "version": "0.5.17",
+      "resolved": "https://registry.npmjs.org/adm-zip/-/adm-zip-0.5.17.tgz",
+      "integrity": "sha512-+Ut8d9LLqwEvHHJl1+PIHqoyDxFgVN847JTVM3Izi3xHDWPE4UtzzXysMZQs64DMcrJfBeS/uoEP4AD3HQHnQQ==",
+      "license": "MIT",
+      "engines": {
+        "node": ">=12.0"
+      }
+    },
     "node_modules/agent-base": {
       "version": "7.1.4",
       "resolved": "https://registry.npmjs.org/agent-base/-/agent-base-7.1.4.tgz",