Replace with "rewind" the "random" button text while holding shift

Describe the feature: I was considering the idea of making the text of the “random” button more dynamic: because of its very cool rewind function using the shift key, I suggest to change its text to “rewind” (or something like that) when holding shift, and turn it back to “random” when shift is released. This can be useful for new players or, in general, for anyone that didn’t noticed this function (and it can be visually nice) because so far it has always been very hidden as a function, so only a few people use it. Also, if you’re considering adding a sort of “hint box” (like on stable) on the main menu, maybe you can add this thing to the list.

[peppy]

May be better to poke @arflyte for this one, to fix the usability-without-keyboard issue at the same time.

[luaneko]

I think instead of pressing shift, long-pressing the random button by mouse would be better for mobile.