Prevents double submit when moving a thread.

I probably moved 1000 of threads and if you double click on the submit button it duplicates the moved thread.

templates/mod/move.html

@@ -1,4 +1,4 @@
-<form action="?/{{ board }}/move/{{ post }}" method="post">
+<form action="?/{{ board }}/move/{{ post }}" method="post" onsubmit="myButton.disabled = true; return true;">
 	<input type="hidden" name="token" value="{{ token }}">
 	<table>
 		<tr>