Adds support for touch events, enabling touch dragging the canvas

[renato-bohler]

Checklist

• [x] The code has been run through pretty yarn run pretty
• [x] The tests pass on CircleCI
• [ ] You have referenced the issue(s) or other PR(s) this fixes/relates-to
• [x] The PR Template has been filled out (see below)
• [x] Had a beer/coffee coke because you are awesome

What?

Adds support for touch events (touchstart, touchmove and touchend). Enables touch dragging the canvas by default.

P.S.: this is already working on logossim, changes applied using patch-package on this PR: https://github.com/renato-bohler/logossim/pull/59

Example:

https://user-images.githubusercontent.com/25781956/114326338-b0049280-9b0a-11eb-909c-2d2340bcfcd6.mp4

Why?

Improves mobile support. Even though it doesn't completely makes touch-based devices supported, this makes it possible for developers to implement full support on their applications (by customizing State).

How?

1. Added 3 touch events to InputType.
2. Changed getActionsForEvent method on ActionEventBus.
3. Changed AbstractDisplacementState to listen for touch events.
4. Added onTouch(Start/End/Move) event handlers on CanvasWidget.
5. Updated the DefaultState.
6. Updated examples.

Feel good image:

[renato-bohler]

This is a mini version of #488 that only enables dragging. The advantage is that this PR could be shipped more easily. Maybe we could work on node dragging/link creation on future versions.

[kobajs]

I need that 👍