Update docs and textcomplete rules for image syntax with size specified

Author: jackycute

public/docs/features.md

@@ -460,6 +460,8 @@ With a reference later in the document defining the URL location:
 
 [id]: https://octodex.github.com/images/dojocat.jpg  "The Dojocat"
 
+![Minion](https://octodex.github.com/images/minion.png =200x200)
+Show the image With given size
 
 ### Footnotes
 

public/js/index.js

@@ -123,6 +123,10 @@ var supportReferrals = [
         text: '![image alt](url "title")',
         search: '![]()'
     },
+    {
+        text: '![image alt](url "title" =WidthxHeight)',
+        search: '![]()'
+    },
     {
         text: '[TOC]',
         search: '[]'