Get level encoding and URL sharing just barely working!

index.html

@@ -106,6 +106,7 @@
         </header>
         <div class="level"><!-- level canvas and any overlays go here --></div>
         <div class="controls">
+            <button id="editor-share-url" type="button">Share?</button>
             <!--
             <p style>
                 Tip: Right click to color drop.<br>