Add feature: LWP3 Device as discussed in [#262](https://github.com/pybricks/support/issues/262)

[NStrijbosch]

Given that bluetooth communication with other devices than the remote was pushed forward on your timeline, I gave this a shot.

These commits will add a starting point to the LWP3Device class as mentioned here: pybricks/support#262 (comment)

This is tested on: Technic Hub/City Hub/Prime Hub, each connects/reads/writes successfully in combination with a City hub and Remote running the stock LEGO firmware. Mario was previously working but can currently not connect see: pybricks/support#442.

I am curious what your view is on this new feature, any feedback is welcome!

I am happy to provide some code examples and/or docs (I didn't know where to place them in this repo)

[laurensvalk]

Thanks for this contribution!

I am happy to provide some code examples and/or docs (I didn't know where to place them in this repo)

Sharing it in a message here would be a good start, to facilitate discussion.

[dlech]

I think Laurens made the same mistake I did on #64 (rebase Nard's branch and try to push it back to Nard's fork). @NStrijbosch can you git push -f your master branch back to GitHub? We might avoid this mistake in the future if you use git checkout -b <name> to give your feature branch a unique name.

[laurensvalk]

I broke this pull request in an attempt to fix it. It seems like this can happen when trying to push back to a fork's master branch. So it seems to help to make a pull request from a branch by a different name, like Mario.