Expose InputMask OnKeyDown event

[davisb10]

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Current behavior
The (keydown) event on the input is not exposed.

Expected behavior
Expose the event as an Output EventEmitter, so it could be used outside the component.

What is the motivation / use case for changing the behavior?

We are currently writing a bill keying module that users quickly type in field from a paper form into the system for future processing. They need to be able to quickly tab around and possibly skip sections if that area is empty. Exposing the keydown would allow us to listen to the tab and if the input is empty, move to the next area.

[davisb10]

@yigitfindikli I have a pull request open for this as well. Not sure why it didn't show it as linked
Pull Request #9719