Expand textarea size

Author: muan

examples/index.html

@@ -19,7 +19,7 @@
         <md-mention class="btn btn-sm">mention</md-mention>
         <md-ref class="btn btn-sm">ref</md-ref>
       </markdown-toolbar>
-      <textarea class="mt-3 d-block width-full" id="textarea"></textarea>
+      <textarea rows="6" class="mt-3 d-block width-full" id="textarea"></textarea>
     </div>
     <!-- script src="../dist/index.umd.js"></script -->
     <script src="https://unpkg.com/@github/markdown-toolbar-element@latest/dist/index.umd.js"></script>