Add experimental CodeMirror plugin

The plugin is incomplete, and currently abandoned. It loads up an
instance of CodeMirror as an editor, and loads the right tiddler into
it, but the work hasn't been done to allow changes to be saved. The
startup time is ridiculously long, which is why I abandoned it.

plugins/tiddlywiki/codemirror/files/tiddlywiki.files

@@ -0,0 +1,19 @@
+{
+	"tiddlers": [
+		{
+			"file": "codemirror.js",
+			"fields": {
+				"type": "application/javascript",
+				"title": "$:/plugins/tiddlywiki/codemirror/codemirror.js",
+				"module-type": "library"
+			}
+		},{
+			"file": "codemirror.css",
+			"fields": {
+				"type": "text/css",
+				"title": "$:/plugins/tiddlywiki/codemirror/codemirror.css",
+				"tags": "[[$:/tags/stylesheet]]"
+			}
+		}
+	]
+}