docs: update docker build command

README.md

@@ -539,16 +539,22 @@ XProxy 默认使用以下配置：
 
 **本地构建**
 
-```
-shell> git clone https://github.com/dnomd343/XProxy.git
-shell> cd ./XProxy/
-shell> docker build -t xproxy .
+```bash
+$ git clone https://github.com/dnomd343/XProxy.git
+$ cd ./XProxy/
+$ docker build -t xproxy .
 ```
 
 **交叉构建**
 
-```
-shell> docker buildx build -t dnomd343/xproxy --platform="linux/amd64,linux/arm64,linux/386,linux/arm/v7" https://github.com/dnomd343/XProxy.git --push
+```bash
+$ git clone https://github.com/dnomd343/XProxy.git
+$ cd ./XProxy/
+$ docker buildx build \
+    -t dnomd343/xproxy \
+    -t ghcr.io/dnomd343/xproxy \
+    -t registry.cn-shenzhen.aliyuncs.com/dnomd343/xproxy \
+    --platform="linux/amd64,linux/arm64,linux/386,linux/arm/v7" . --push
 ```
 
 ## 许可证