docs(editor): improve editor-app build documentation and add build:rapier2d script

- Add `pnpm build:rapier2d` command to automate Rapier2D WASM build process
- Fix gen-src.mjs path to correctly locate thirdparty/rapier.js
- Update init.ts to work with new wasm-pack web target (auto-initialization)
- Fix behavior-tree-editor build config for asset-system dependency
- Update README_CN.md and README.md with simplified build instructions

packages/editor/plugins/behavior-tree-editor/tsconfig.build.json

@@ -8,7 +8,10 @@
         "rootDir": "./src",
         "jsx": "react-jsx",
         "skipLibCheck": true,
-        "moduleResolution": "bundler"
+        "moduleResolution": "bundler",
+        "paths": {
+            "@esengine/asset-system": ["../../../engine/asset-system/src"]
+        }
     },
     "include": ["src/**/*"],
     "exclude": ["node_modules", "dist", "**/*.test.ts"]