Add field gesture and field images for the different gestures (#803)

fieldeditors/extensions.ts

@@ -1,10 +1,15 @@
 /// <reference path="../node_modules/pxt-core/built/pxteditor.d.ts"/>
 /// <reference path="../node_modules/pxt-core/built/pxtsim.d.ts"/>
 
+import { FieldGestures } from "./field_gestures";
+
 pxt.editor.initFieldExtensionsAsync = function (opts: pxt.editor.FieldExtensionOptions): Promise<pxt.editor.FieldExtensionResult> {
     pxt.debug('loading pxt-microbit field editors...')
     const res: pxt.editor.FieldExtensionResult = {
-        fieldEditors: []
+        fieldEditors: [{
+            selector: "gestures",
+            editor: FieldGestures
+        }]
     };
     return Promise.resolve<pxt.editor.FieldExtensionResult>(res);
 }