enabled caching via .htaccess

webmails/roundcube/Dockerfile

@@ -38,7 +38,8 @@ RUN apt-get update && apt-get install -y \
  && sed -i 's,^php_value.*post_max_size,#&,g' .htaccess \
  && sed -i 's,^php_value.*upload_max_filesize,#&,g' .htaccess \
  && chown -R www-data: logs temp \
- && rm -rf /var/lib/apt/lists
+ && rm -rf /var/lib/apt/lists \
+ && a2enmod rewrite deflate expires headers
 
 COPY php.ini /php.ini
 COPY config.inc.php /var/www/html/config/