fix small ui issues

Author: AsakiAsako

_sass/_gitalk.scss

@@ -204,6 +204,7 @@
   .markdown-body pre {
     padding: 16px;
     overflow: auto;
+    -webkit-overflow-scrolling: touch;
     font-size: 85%;
     line-height: 1.45;
     background-color: #f6f8fa;
@@ -700,6 +701,7 @@
     border-radius: 5px;
     border: 1px solid $divider-color;
     overflow: auto;
+    -webkit-overflow-scrolling: touch;
     -webkit-transition: all ease 0.25s;
     transition: all ease 0.25s;
 

_sass/_highlights.scss

@@ -16,7 +16,8 @@ pre.highlight {
   border: 1px solid $oc-gray-3;
   border-radius: 3px;
   margin: 1em 0;
-  overflow: scroll;
+  overflow: auto;
+  -webkit-overflow-scrolling: touch;
 }
 
 .highlight  { background: $oc-gray-0; }

style.scss

@@ -180,6 +180,7 @@ dt {
   float: left;
   width: $dt-width;
   overflow: auto;
+  -webkit-overflow-scrolling: touch;
   clear: left;
   text-align: right;
   white-space: nowrap;