Maintainer for the stm32f30x-hal repository

[eldruin]

The stm32f30x-hal repository would benefit from an additional maintainer (japaric/stm32f30x-hal#22).
In this meeting it was proposed that the HAL team would maintain it but in the team list I cannot see that this is the case. Maybe this slip through or so.
Nowadays there is also the stm32-rs org, which is also an option.
Being stm32f30x-hal "the canonical implementation" I would understand extra caution here.

[jonas-schievink]

That HAL is now mostly obsolete and replaced by https://github.com/stm32-rs/stm32f3xx-hal, so closing.