* Remove traits section now that we have embedded-hal-async and refer to
it.
* Explanation that embassy is multiple things.
* Bootloader description image
* Less generics on bootloader. Keep PAGE_SIZE as a common multiple of
DFU and ACTIVE page sizes.
* Document restriction
* Add unit tests for different page sizes
* Add flash drivers for L0, L1, L4, WB and WL. Not tested for WB, but
should be similar to WL.
* Add embassy-boot-stm32 for bootloading on STM32.
* Add flash examples and bootloader examples
* Update stm32-data
