Add ESLint plugin

[cjoudrey]

Although we aren't defining the rules the way ESLint expects, we might be able to add a module that makes the linter work with ESLint.

For example: https://github.com/azeemba/eslint-plugin-json/blob/d2d48e30e17d9d4e7c62455ceffbd8338cd5b083/lib/index.js#L25

Another example: https://github.com/apollographql/eslint-plugin-graphql