STM32: Support new dev boards

[hierophect]

To be added:

• PYB LR Nano V2 [F411]
• F411 "Blackpill", generic [F411]
• Meowbit [F401]

[hierophect]

@ladyada do you have preferred names for each of these? Folder type names like feather_stm32f405_express/.

[ladyada]

no preference as long as they are unique enough to avoid future confusion. you can get inspiration from the other folders :)

[ladyada]

matek betaflight controllers use stm32f405
https://www.amazon.com/MATEKSYS-F405-STD-Flight-Controller-STM32F405/dp/B079CN4QX3

https://www.banggood.com/Matek-F405-OSD-BetaFlight-STM32F405-Flight-Controller-Built-in-OSD-Inverter-for-RC-Multirotor-FPV-Racing-Drone-p-1141282.html

[hierophect]

@ladyada I'll need some new VIDs and PIDs for these boards, correct?

[ladyada]

PYB Nano v2 VID 0x239A PID 0x0067 # bootloader
PID 0x8067 # arduino
PID 0x8068 # circuitpython

F411 BlackPill VID 0x239A PID 0x0069 # bootloader
PID 0x8069 # arduino
PID 0x806A # circuitpython

[hierophect]

@ladyada thanks!