Update ESLint

[newswim]

The .eslintrc file is pretty out of date.

# run linter
> yarn lint
$ eslint .
/Users/dm/github/CommonGarden/Grow-IoT/packages/graphql-api/node_modules/cors/.eslintrc:
    Configuration for rule "quotes" is invalid:
    Severity should be one of the following: 0 = off, 1 = warn, 2 = error (you passed '"single"').

Error: /Users/dm/github/CommonGarden/Grow-IoT/packages/graphql-api/node_modules/cors/.eslintrc:
    Configuration for rule "quotes" is invalid:
    Severity should be one of the following: 0 = off, 1 = warn, 2 = error (you passed '"single"').

# the bigger fish to fry
(node:9169) DeprecationWarning: [eslint] The 'ecmaFeatures' config file property is deprecated, and has no effect. (found in /Users/dm/github/CommonGarden/Grow-IoT/.eslintrc)

Improvement plan

1. Update eslint in devDependencies, port/replace existing configuration to follow newer practices.

(or) 2. Switch to prettier.

• Pro: Widely used, integrates with eslint, format-on-save is the 💩, lots of language support (eg. markdown, graphql schemas, json files...)
• Con: Can be a somewhat 💩-y experience for Vim users (although there's at least one popular package that looks fine on the surface).

[JakeHartnell]

eslint has been updated, we should use it more.