#### Is this adding or improving a _feature_ or fixing a _bug_?
Example.
#### What's the new behavior?
Adds a new example that is an input event logger, for more easily seeing which input/keyboard/selection events are firing when editing in a Slate editor.
#### Have you checked that...?
* [x] The new code matches the existing patterns and styles.
* [x] The tests pass with `yarn test`.
* [x] The linter passes with `yarn lint`. (Fix errors with `yarn prettier`.)
* [x] The relevant examples still work. (Run examples with `yarn watch`.)
