Re-add event listeners to images after a finished VE edit

Currently, if VisualEditor saved an edit, it replaces the current content
with the new content, which removes all already added event listeners, e.g.
on thumbs, added by MMV.

Add a new hook handler to the postEdit JavaScript hook to re-add all event
handlers to the thumb images to cover this case and enable MMV on a page
after a finished VE edit.

Bug: T97010
Change-Id: Ic1ee0b52265363978640358510cab89db4de2bb8

resources/mmv/mmv.bootstrap.js

@@ -61,9 +61,13 @@
 
 		this.thumbsReadyDeferred = $.Deferred();
 		this.thumbs = [];
+		this.$thumbs = null; // will be set by processThumbs
 
-		this.$thumbs = $( '.gallery .image img, a.image img, #file a img' );
+		// find and setup all thumbs on this page
 		this.processThumbs();
+		// repeat this, if the page has changed, e.g. because of a
+		// finished VisualEditor edit.
+		mw.hook( 'postEdit' ).add( $.proxy( this, 'processThumbs' ) );
 
 		this.browserHistory = window.history;
 	}
@@ -145,6 +149,8 @@
 	MMVB.processThumbs = function () {
 		var bs = this;
 
+		this.$thumbs = $( '.gallery .image img, a.image img, #file a img' );
+
 		// if this breaks in IE8, see https://github.com/ebryn/backburner.js/pull/50
 		// but it probably won't since there is a catch further up the chain
 		try {