Replace all warns with errors

[ismail-syed]

We pretty much treat all warn as error anyways, let's make this explicit.

[GoodForOneFare]

Context:

*Chris*
the idea was that all lint errors were errors

we only made some warnings because errors were obnoxious in Atom at one point :stuck_out_tongue:

if we let warnings through then we a) need to have a harder rule on what is a warning and what is an error, and b) have some criteria for ignorable warnings

both seem really hard to do well so I would rather just follow the stylelint approach here (all things are errors)

if we have linting warnings we think are usuablly ignorable we should turn the rule off

*Tyler*
can we reclassify everything in our linting config as errors then?

if you’re running eslint outside the context of sewing-kit but are using the config then you have to explicitly set `max-warnings` on your lint task

which is a little obscure

*Chris*
I’d be happy with that