Update README for webgl plugin.

README-ZH.md

 默认的逻辑是在界面静止时将帧率降低为15，在界面变动时将帧率提高至60。
 如果您需要修改帧率升高或降低时的行为，请将`Window.onFrameRateSpeedUp`和/或`Window.onFrameRateCoolDown`设置为您自己的函数。
 
+#### 八、WebGL分辨率调整插件
+因为浏览器中Canvas的宽高和其在显示器上的像素数可能不一致，所以构建出的WebGL程序中画面可能会模糊。
+插件`Plugins/platform/webgl/UIWidgetsCanvasDevicePixelRatio.jslib`解决了这个问题。
+如果您因为任何原因需要禁止此插件，请在Project面板中选中该插件，在Inspector面板中的Define Constraints参数中，填入一个未被定义的宏名称。
+
 ## 调试UIWidgets应用程序
 
 #### 定义UIWidgets_DEBUG

README.md

 To build an App that is able to adjust the frame rate automatically, please open Project Settings, and in the Quality tab, set the "V Sync Count" option of the target platform to "Don't Sync".
 The default logic is to set the frame rate to 15 when the screen is static, and change the frame rate to 60 whenever the screen changes.
 If you would like to modify the behavior of speeding up or cooling down the frame rate, please set `Window.onFrameRateSpeedUp` and/or `Window.onFrameRateCoolDown` to your own functions.
+
+#### WebGL Device Pixel Ratio Plugin
+The width and height of the Canvas in browser may differ from the number of pixels the Canvas occupies on the screen.
+Therefore, the image may blur in the builded WebGL program.
+The Plugin `Plugins/platform/webgl/UIWidgetsCanvasDevicePixelRatio.jslib` solves this issue.
+If you need to disable this plugin for any reason, please select this plugin in the **Project** panel, and put an arbitrary undefined macro name in the **Define Constraints** field in the **Inspector** panel.
  
 ## Debug UIWidgets Application