* Add eslint to dev dependancies so it gets installed for the repo

yarn add --dev eslint babel-eslint eslint-plugin-reac

project specific version of eslint, you can globally install eslint-cli
if you want the global runtime, or add .bin to your path

* fix eslint errors about inconsitent returns

* eslint ignore the same as git ignore. allows for eslint .

* Add editorconfig file so everyones editor will be setup to follow the same standards

It took me ages to get Mastodon set up with the tests passing because
the environment variables I needed to define weren't documented and I
had to work them out one at a time.

This change adds a .env.test file, and makes it so it isn't ignored by
git. I think it makes sense for the .env.test file to be in git, since
there's nothing secret in it, but other approaches would be to have a
.env.test.sample (like the corresponding one for production), or to set
these values in a test helper, or to adapt the tests to work with
environments other than this one. I'd be happy to make these changes if
that would be preferred.

Being able to get set up and run the tests is a pretty important part of
being able to contribute to Mastodon (or your test coverage with
suffer!), so having some sort of solution like this one is vital.