add develop.md

DEVELOP.md

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+# Development Guide
+
+1. install http-server to enable debug at local.
+
+```bash
+npm install -g http-server
+```
+2. run `npm install` to build the project.
+3. in `./` folder, use `http-server` to start server
+4. open the following link to debug.
+   please note, the server address should be checked in the source code of `xxx.html`!
+```
+http://127.0.0.1:8080/test/ws.html
+http://127.0.0.1:8080/test/http.html
+```