Adds a javascript widget tutorial to the dev tiddlywiki edition (#7016)

* Initial widget tutorials extracted from https://btheado.github.io/tw-widget-tutorial/

* Fixes for refresh behavior change

editions/dev/tiddlers/javascript-widget-tutorial/Hello World demo.tid

@@ -0,0 +1,23 @@
+created: 20190201114718313
+modified: 20190201231556294
+tags: 
+title: Hello World demo
+type: text/vnd.tiddlywiki
+
+<!-- The innerwiki doesn't refresh on its own when tiddlers on the outside change, so use the list widget to force a dependency -->
+<$list name=refresh filter=[[hello.js]get[text]]>
+<$innerwiki width="600" height="400" style="width:100%;">
+	<$data title="$:/DefaultTiddlers" text="[[hello world widget]]"/>
+	<$data $tiddler=hello.js/>
+	<$data title="hello world widget" text="""
+```
+<$hello/>
+```
+
+Renders as:
+
+<$hello/>
+"""/>
+
+</$innerwiki>
+</$list>