Update README (#1101)

### What problem does this PR solve?

Update README for build from source.

### Type of change

- [x] Documentation Update

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

README.md

@@ -297,7 +297,7 @@ To launch the service from source:
    $ cd web
    $ npm install --registry=https://registry.npmmirror.com --force
    $ vim .umirc.ts
-   # Update proxy.target to 127.0.0.1:9380
+   # Update proxy.target to http://127.0.0.1:9380
    $ npm run dev 
    ```
 

README_zh.md

@@ -266,7 +266,7 @@ $ bash ./entrypoint.sh
 $ cd web
 $ npm install --registry=https://registry.npmmirror.com --force
 $ vim .umirc.ts
-# 修改proxy.target为127.0.0.1:9380
+# 修改proxy.target为http://127.0.0.1:9380
 $ npm run dev 
 ```