Add press duration to PressedActionInfo

[phalasz]

Add key press duration to the PressedActionInfo's EventInfo.
Resolves #32

I've included an internal minOf implementation. This can be removed if the required go version can be bumped to 1.21.0+ which has a built-in min function with variadic parameter support.

[quasilyte]

I'll take a closer look tomorrow, but I think it looks good.
I would like to mention that the duration is in frames, as it may not be obvious unless you're expecting it to have the same API as inpututil.

[phalasz]

Sure, no worries. Let me know if changes are needed or if there are improvements that should be made.

[quasilyte]

I could do a couple of nits, but I don't see a reason to do it. :)
This code is good.
I'll fix a couple of comment-related issues like double spaces myself.

Thank you for the implementation of this feature. 👍

[quasilyte]

We may want to add something that uses this feature in the examples though.
It could be a new example or some extension to an already existing example.