Update alpha is transparency.

README-ZH.md

 如果您希望切换到Google版本的表情，请按如下步骤操作：
 
 1. 拷贝`Runtime/Resources/backup~/EmojiGoogle.png`到`Runtime/Resources/images`目录。
-2. 在**Project**面板中，找到`EmojiGoogle`资源，在**Inspector**面板中，将**Max Size**更改为4096，并取消**Generate Mipmaps**选项前的对勾。
+2. 在**Project**面板中，找到`EmojiGoogle`资源，在**Inspector**面板中，将**Max Size**更改为4096，取消选中**Generate Mipmaps**，并选中**Alpha Is Transparency**。
 3. 在您的代码中继承`UIWidgetsPanel`的类的`OnEnable()`函数中，添加如下代码
 
 ```csharp

README.md

 To switch to Google version of emoji, please follow the following steps:
 
 1. Copy `Runtime/Resources/backup~/EmojiGoogle.png` to `Runtime/Resources/images` folder.
-2. In the **Project** panel, find and select `EmojiGoogle` asset, and in the **Inspector** panel, change **Max Size** to 4096, and disable **Generate Mipmaps**.
+2. In the **Project** panel, find and select `EmojiGoogle` asset, and in the **Inspector** panel, change **Max Size** to 4096, disable **Generate Mipmaps**, and enable **Alpha Is Transparency**.
 3. In the `OnEnable()` function in your class overriding `UIWidgetsPanel`, add the following code
 
 ```csharp

Runtime/Resources/images/EmojiIOS13.2.png.meta

   spriteBorder: {x: 0, y: 0, z: 0, w: 0}
   spriteGenerateFallbackPhysicsShape: 1
   alphaUsage: 1
-  alphaIsTransparency: 0
+  alphaIsTransparency: 1
   spriteTessellationDetail: -1
   textureType: 0
   textureShape: 1