chore(README): Update main development version

Author: MSDNicrosoft

README.md

@@ -65,7 +65,7 @@ commands into the JSON as new buttons are created and loads the JSON at the next
 
 ## Support
 
-Current main development for Minecraft version: `1.21.5`
+Current main development for Minecraft version: `1.21.8`
 
 And use `preprocess` to be compatible with the following versions.
 

README_ZH_CN.md

@@ -64,7 +64,7 @@ Command GUI Buttons 是 Minecraft 的 Fabric 模组，允许用户在其客户
 
 ### 支持
 
-当前主开发版本: `1.21.5`
+当前主开发版本: `1.21.8`
 
 并且使用 `预处理` 来兼容下列版本。