在根目录下创建 .htaccess 文件，有的空间会自带
写入如下规则：
<IfModule mod_rewrite.c>
RewriteEngine On
RewriteBase /
# en.xxxx.com
RewriteCond %{HTTP_HOST} ^en\.xxxx\.com$ [NC]
RewriteCond %{REQUEST_URI} !^/en/
RewriteRule ^(.*)$ en/$1?Rewrite [L,QSA]
# de.xxxx.com
RewriteCond %{HTTP_HOST} ^en\.xxxx\.com$ [NC]
RewriteCond %{REQUEST_URI} !^/en/
RewriteRule ^(.*)$ en/$1?Rewrite [L,QSA]
</IfModule>