readme update

README.md

@@ -31,10 +31,16 @@ xlswriter is a PHP C Extension that can be used to write text, numbers, formulas
 * FreeBSD License.
 * The only dependency is on zlib.
 
+#### Documents
+
 [文档|Documents](https://xlswriter-docs.viest.me/)
 
 [![pecl](https://github.com/viest/php-excel-writer/blob/master/resource/pecl.png)](https://pecl.php.net/package/xlswriter)
 
+#### Exchange group
+
+<img width="80" src="https://github.com/viest/php-excel-writer/blob/master/resource/qq.jpg"/>
+
 #### License
 
 FreeBSD license