Consider adding an initial dialog to enable haptic interactions

[jbphet]

We received some feedback in today's review meeting that the initial haptic vibration seemed a little delayed in the HTML5 prototype of some early vibrational haptics support. This is probably because of some sort of an auto-play policy, similar to what we've seen for sound, that prevents haptics from being activated until the user interacts with the web page.

If this continues to be a problem, we may want to add a dialog that says something like "Click here to activate vibrational haptics."

[jbphet]

I've assigned this to myself, but since it's a pretty significant UX change, I think I'll implement some other aspects of the haptics first, then have the team test it out and decide if it's a significant enough issue that we should add this dialog.

[jbphet]

I was just testing haptic vibration using a Samsung Tab S7, and noticed that indeed, if I load the HTML5 version and start dragging a side or a vertex, no vibration is felt until I release it and do it again. This seems like it could be a problem for our testing. I think I might try adding a query parameter and a dialog and see how that works. If it's a reasonable experience, I'll run it by the design team.

[jbphet]

I've added a dialog and put it behind a query parameter. The parameter is a flag named showInitialTouchDialog. I'll review this in the next quad+haptics meeting.