Weex core operating principle analysis

1. Weex consists of three parts:

JS Bridge Render Dom
WXBridgeManager WXRenderManager WXDomManager
#### 2. Weex operating mechanism flowchart
#### 3. Operating principles of WEEX

Managed by WXSDKManager, JS Bridge and Dom run in separate HandlerThreads, while Render runs in the UI thread. JS Bridge is mainly used for two-way communication with JS end implementation

For example, the DOM structure of the JS side is passed to the DOM thread. The Dom is used to handle parsing, mapping, adding, and so on to the Dom, and then notifies the UI thread to update it. Render is responsible for rendering the DOM in the UI thread.