Show a warning message if ventoy.json is in UCS-2 encoding. (#1125)

ventoy.json must in UTF-8 encoding. The BOM is auto skipped if exist.

INSTALL/grub/grub.cfg

@@ -2178,12 +2178,19 @@ fi
 
 if [ -n "$VTOY_PLUGIN_SYNTAX_ERROR" ]; then
     clear
-    echo -e "\n Syntax error detected in ventoy.json, please check! \n"
-    echo -e " ventoy.json 文件中有语法错误，所有配置都不会生效，请检查！\n"
+    if [ -n "$VTOY_PLUGIN_ENCODE_ERROR" ]; then
+        echo -e "\n Encoding type for ventoy.json is not supported, please convert to UTF-8.\n"
+        echo -e " ventoy.json 文件编码格式不支持，请转换为 UTF-8 编码格式！\n"
+    else
+        echo -e "\n Syntax error detected in ventoy.json, please check! \n"
+        echo -e " ventoy.json 文件中有语法错误，所有配置都不会生效，请检查！\n"         
+    fi
+
     echo -e "\n press ENTER to continue (请按 回车 键继续) ..."
-    read vtInputKey 
+    read vtInputKey
 fi
 
+
 for vtTFile in ventoy.json ventoy_grub.cfg; do
     if [ -f $vtoy_efi_part/ventoy/$vtTFile ]; then
         clear