Make monitor only send key on press, not on release

[LelouBil]

Fixes #660

[SergioGasquez]

Hi! Thanks for your contribution! Do you mind rebasing/fixing the rustfmt error and sharing your testing results?

This might be an improvement but, as you mentioned, there are differences between os/terminals, so I would like to test it properly.

[LelouBil]

Test results, works for :

• IntelliJ/RustRover terminal
• PuTTY Serial
• Old Windows terminal (conhost.exe)
• New Windows terminal

Works is : key press sends character, release does not. Key repetition works if held for a bit

I think it's fine, I can't test it on Linux now, but since it works with PuTTY I assume it will work with anything. PuTTY is the most basic serial client you can find.

I might also try tracking the issue from some kind of upstream dependency I think, that added difficulty debugging this : the fact that on the new Windows terminal and rustrover terminal key press and release events were sent only on key press.

But for the espflash issue, I think we're good

[SergioGasquez]

LGTM! Thanks for the PR!