Enable mouse rotate, pan, and zoom with TrackballControls

src/dyna3.litcoffee

@@ -3,7 +3,9 @@
 When you load dyna3, you should initially see a three-dimensional coordinate system with labeled axes.
 ```javascript
 
-    import {threeLoaded, three as J3} from './externals.js'
+    import {threeLoaded,
+        three as J3,
+        TrackballControls as J3x} from './externals.js'
 
     LTx = { dashed: true, plain: false }
 
@@ -48,7 +50,11 @@ When you load dyna3, you should initially see a three-dimensional coordinate sys
         camera = new J3.PerspectiveCamera 75, rwd/rht, 0.1, 1000
         camera.position.z = 5
 
-        renderer.render scene, camera
+        controls = new J3x.TrackballControls camera, renderer.domElement
+
+        renderer.setAnimationLoop ->
+           controls.update()
+           renderer.render scene,camera
 
     threeLoaded.then main
 ```