Add pressed and released buttons

[StaterZ]

Icons are based of delapouite/button-finger.svg

Beyond that, have some icons!

button-pressed	button-released	delapouite/button-finger for reference

[luizbills]

Perhaps the button press could be even lower.

[StaterZ]

@luizbills It was something I considered when I was creating them as well. However I thought the sides started looking odd when it went too deep down. I made an alternate version for your consideration. This one is more clear, but I'm not fully sure which one I prefer honestly :/

[StaterZ]

Added the even more pressed down button version suggested by @luizbills to the pull request.
I kept the old button-pressed as button-half-pressed as it's based the height of delapouite/button-finger and may therefore still be of use to someone.

button-pressed	button-half-pressed	button-released	delapouite/button-finger for reference