Check repo scripts with shellcheck, flake8

[ZLLentz]

We use these scripts a lot, lets make sure they are doing all the normal good practices.
My plan is to add a CI job that simply runs shellcheck and flake8 on the contents of deploy and scripts as appropriate.

In the context of some items which may be better as-is for this use case:

Can also add a # shellcheck disable=ERRID to explicitly say "I'm ok with this"
Originally posted by @klauer in #239 (comment)

[klauer]

I have shellcheck done in pre-commit for shared-dotfiles - it may be of use:
https://github.com/pcdshub/shared-dotfiles/blob/master/.pre-commit-config.yaml