fix(installer): 添加pwsh安装前检查避免重复安装

如果pwsh已安装则跳过安装步骤，避免重复安装

Author: mudssky

linux/ubuntu/installer/install_pwsh.sh

@@ -1,5 +1,11 @@
 #!/bin/bash
 
+# 判断pwsh是否已安装
+if command -v pwsh &> /dev/null
+then
+    echo "pwsh found, skip install"
+    exit 0
+fi
 
 ###################################
 # Prerequisites