CI, JLCPCB part numbers, and README improvements

[flaviut]

This is a bit of a big PR, and I'd be happy to split it up (or you could cherry-pick as appropriate) as you'd like.

• I've added JLCPCB part numbers, saving me the time and hassle of assembling everything
• I've added continuous integration--this is a very common concept in software engineering where error-checking and release creation process is fully automated. At the moment, it's complaining about a bunch of errors, so I've disabled that part
• I've updated readme with additional information

[crteensy]

Sorry for being a bit late here. I'm currently on vacation and will take a close look when I'm back

[flaviut]

take your time and enjoy your vacation :)

maybe by the time you get back, I'll have received boards to test if I messed anything up.

[flaviut]

I've had JLCPCB produce and deliver the boards:

My scope is only 100MHz and my crystal only 12MHz, but everything checks out:

I ended up going with this can instead of the one in the BOM--not that that's relevant to this PR.