feat(admin): 新增 markdown 编辑器支持，integrate EasyMDE markdown editor for admin interface

Introduce the EasyMDE markdown editor into the admin interface, providing enhanced
markdown editing capabilities. This integration caters to users preferring a dedicated
markdown editor with additional features and a streamlined user experience.

app/common.php

@@ -112,6 +112,7 @@ if (!function_exists('auth')) {
         return match ($editor_type) {
             'ckeditor' => "<textarea name='{$name}' rows='20' class='layui-textarea editor' placeholder='{$placeholder}'>{$detail}</textarea>",
             'ueditor'  => "<script type='text/plain' id='{$name}' name='{$name}' class='editor' data-content='{$detail}'></script>",
+            'EasyMDE'  => "<textarea id='{$name}' class='editor' name='{$name}'>{$detail}</textarea>",
             default    => "<div class='wangEditor_div'><textarea name='{$name}' rows='20' class='layui-textarea editor layui-hide'>{$detail}</textarea><div id='editor_toolbar_{$name}'></div><div id='editor_{$name}' style='height: 300px'></div></div>",
         };
     }