Add mte to the Markdown editor to enhance table editing, e.g. https://susisu.github.io/mte-demo/ (#1)

Signed-off-by: Seanly Liu <seanly@opsbox.dev>

static/js/markdown.js

@@ -113,6 +113,7 @@ $(function () {
             });
             
             window.isLoad = true;
+            this.tableEditor = TableEditor.initTableEditor(this.cm)
         },
         onchange: function () {
             resetEditorChanged(true);