Create shared eslint config for projects and modules

[devinreams]

A suggestion from @pdehaan at mozilla-lockwise/lockbox-datastore#34 (review) to consider:

a custom eslint-config-lockbox and/or eslint-plugin-lockbox so you can share ESLint configs between repos for cross repo consistency

[pdehaan]

If somebody with GitHub powers can create an empty mozilla-lockbox/eslint-plugin-lockbox, I can take a stab at creating a shared ESLint config (if this is something you want to pursue).

[devinreams]

I think it's something we'll want. There is project-specific stuff we'd still need to consider including/excluding. For example "browser" stuff and a11y linitng would not be necessary for the datastore...

https://github.com/mozilla-lockbox/eslint-plugin-mozilla-lockbox

[pdehaan]

Initial PR for shared plugin rules at mozilla-lockwise/eslint-plugin-mozilla-lockbox#1.
It was working locally for me, but I had to do a bit of package.json hackery to install from my GitHub PR branch since it hasn't been published to npm, so it may take a bit of fiddling once we get the PR merged and published.