LPUART implementation in serial.rs

[rgw3d]

I'd like to be able to use the lpuart capability on my STM32L496, and noticed that it wasn't already implemented!

I might make an effort to do this myself, but was curious if someone has thought about this already and had insight as to why it wasn't implemented already.

[romixlab]

Needed the same thing, came up with this, not yet tested though: romixlab@1cf3332

[romixlab]

This works: romixlab@3a1b7be

[korken89]

The answer to not being implemented yet is simple, none of the maintainers has needed it yet :)
We would welcome a PR adding the LPUART.

[jglauche]

This works: romixlab@3a1b7be

would you like to make this a PR? I'm in need of the same thing. I don't want to work on it too if you plan to do this soonish.

[rgw3d]

I have not been able to work on this at all yet

[romixlab]

Finally got some time to work on this, PR is open.