Please add b2 core

[SpyMasterP]

The core b2 (BBC Micro) was recently released just before RetroArch v1.20.0 was cut.

It's a computer system released in the early 80s in the UK similar to the C64, and has its own unique collection of software and games.

It's the only system I miss from switching from the RG300 to the Miyoo Mini.

I would really appreciate if it could be considered for inclusion.