Add plugin manager and example plugin system

Introduces a plugin manager (OB11PluginMangerAdapter) for dynamic plugin loading, initialization, and event handling. Adds an example plugin with configuration files and updates related code to support plugin directory detection and loading. Refactors plugin adapter logic for extensibility and modularity.

src/example-plugin/package.json

@@ -0,0 +1,10 @@
+{
+  "name": "advanced-plugin",
+  "version": "1.0.0",
+  "type": "module",
+  "main": "index.mjs",
+  "description": "一个高级的 NapCat 插件示例",
+  "scripts": {
+    "build": "vite build"
+  }
+}