fix languages in sigs

content/en/sig/_index.md

 +++
 title = "SIG(Special Interest Group)"
+summary = "SIGs are project teams which maintain one or more projects in the community."
 +++

content/zh/sig/_index.md

 +++
 title = "SIG（项目组）"
+summary = "SIGs是社区根据领域划分的各个领域的兴趣小组，每一个小组会根据情况维护社区一个或者多个项目。"
 +++

themes/project/layouts/sig/list.html

@@ -18,7 +18,7 @@
         <div id="content">
             <div class="container">
                 <div class="row">
-                    <div class="col-md-12"> SIGs是社区根据领域划分的各个领域的兴趣小组，每一个小组会根据情况维护社区一个或者多个项目。</div>
+                    <div class="col-md-12">{{ .Summary }}</div>
                     <div class="col-md-12" id="sigSection" style="margin-bottom: 30px;">
                             {{ range where $.Page.Site.Pages "Type" "sig" }}
                             {{ if .Params }}