Try: Add component for handling keyboard events

[aduth]

Fixes #1850
Supersedes #1908
Related: #1943

This pull request explores adding a new KeyboardEvents component to assist in handling keyboard events.

<KeyboardShorcuts shortcuts={ {
	'mod+a': this.setAllSelected,
} } />

See full README.md documentation

Implementation notes:

Currently, it is implemented to capture keyboard events globally, but I expect this could be further enhanced in the future to add scoping to a specific element context by optionally supporting children of KeyboardShortcuts, where a combination of ref, findDOMNode, and renderedNode.contains( event.target ) confirms that the keyboard event occurred within the rendered children.

Testing instructions:

Verify that there is no regression in "Select All" keyboard behavior (#1211).

[ellatrix]

This looks great to me. 👍

[westonruter]

It's beautiful. 😍