[FR] Upload Bootloader for SKR3 and SKR3 EZ

[admilsonmarques]

Hi, this week BTT sent me the hex files for the original bootload of these two boards and I'd like to add them here since this repo is well recommended for such things, do you think it is possible for me to do this?

[r6e]

@admilsonmarques I could really use this; could you submit a PR here to add them? Even if they're not merged, it'd make them available for folks.

Alternatively; if you could upload them somewhere, it'd be hugely appreciated. Thanks!