Update for SKR Mini E3, Add SKR Pro Bootloader

This release updates the bootloader and hid-flash tool so that it can properly deal with the 2K flash pages on the STM32F1 variant the SKR Mini E3 uses. See the previous release for details between the button and no button versions. NOTE: If you flashed the previous release, please make sure you navigate to ~/klipper/lib/hidflash and issue a make clean command. If you do not then the flash may fail.

Also added is a bootloader for the BTT SKR Pro.

As with before, these bootloaders must be flashed using a programmer. With the SKR Pro it is possible to flash via UART using the system bootloader.

The usual disclaimers apply to these binaries, use at your own risk and I am in no way responsible for bricked devices, magic smoke, fires, explosions, etc.