[FR] Add the source code used for building firmware

[medisoft]

Is your feature request related to a problem? Please describe.
I'm trying to add support for the filament sensor to the board, because the available firmwares only include bltouch, but the filament sensor is not there. I downloaded latest version of Marlin, 2.0.x, and 2.1.x, normal and bugfixes, and used the configuration for Ender 3 Pro with BTT SKT Mini E3 V3.0. Everything builds OK, but when I try to flash the firmware, the printer stays with blank screen and the firmware.bin is not moved to firmware.cur, after that, the printer don't boot anymore, unless I flash the https://github.com/bigtreetech/BIGTREETECH-SKR-mini-E3/tree/master/firmware/V3.0/Marlin/firmware-ender3.bin or any of the other firmwares in that repo.

Describe the solution you'd like
So I think you should make the source you used available in the same folder as the binary files, so that if one needs to add or remove something, it is possible.

Describe alternatives you've considered
I built the firmware using the configurations at https://github.com/MarlinFirmware/Configurations/tree/bugfix-2.1.x/config/examples/Creality/Ender-3%20Pro/BigTreeTech%20SKR%20Mini%20E3%203.0, for release, imported and bugfix, for 2.0.x and 2.1.x, and always the same result

[yasavvym8]

I'd also appreciate it if they actually kept their repository up to date

[john-clark]

No current support = no future purchases.