Mention in studio UI that %%USER_ID%% works

AUTHORS

@@ -86,5 +86,6 @@ Yarko Tymciurak <yarkot1@gmail.com>
 Miles Steele <miles@milessteele.com>
 Kevin Luo <kevluo@edx.org>
 Akshay Jagadeesh <akjags@gmail.com>
+Nick Parlante <nick.parlante@cs.stanford.edu>
 Marko Seric <marko.seric@math.uzh.ch>
 Felipe Montoya <felipe.montoya@edunext.co>

cms/templates/component.html

@@ -11,6 +11,7 @@
 		<div class="component-edit-header">
   			<span class="component-name"></span>
   	  		<ul class="nav-edit-modes">
+				<span class="help-text" style="color: #ddd;font-size:small;">${_("%%USER_ID%% in text expands, e.g. 2A6B...")}</span>
   	  			<li id="editor-mode" class="mode active-mode" aria-controls="editor-tab" role="tab">
   	  				<a href="#">${_("Editor")}</a>
 	  			</li>