Move KeyboardDragListener to scenery

[zepumph]

It makes the most sense for a base listener like this to live in scenery.

[zepumph]

Because of work done in #884, we are ready to move this over to scenery now. Marking high so that we can write scenery a11y examples of it before CSUN.

[zepumph]

@twant perhaps next week we can work on this together. I don't want to confuse you too much too early, but it could be nice to have you along for some common code work. (what do you think @jessegreenberg?)

[twant]

@zepumph sounds good to me to take a look at it this week! Talk to you soon.

[zepumph]

@twant and I used

copy-history-to-different-repo.sh js/accessibility/listeners/KeyboardDragListener.js ../scenery

To copy the history of the file over to scenery.

We then converted the 5 usages to point to the scenery version. The doc we added was to try to make sure that users know that the file is heavily reliant on AXON/timer.

@jessegreenberg will you please review.

[zepumph]

@twant pointed out that she was getting an error trying to use this in the built version of scenery. After investigation it looks like we weren't adding it the SCENERY/main.js. @jessegreenberg over to you.

[jessegreenberg]

This is very old, big ping to myself to review while I do #1054.

[jessegreenberg]

Great to have this in scenery. Usages look great. Closing