enforce JS import ordering

[kadamwhite]

In #75 @igmoweb proposed the addition of the sort-imports ESLint rule, to control the ordering of modules we import into our code.

In a Slack thread @rmccue further proposed that we conform to a general ordering of absolute, then relative, then side effects (e.g. importing a CSS file to ensure it gets included in the build, but not using the return of that import), with a blank line between each, and each section alphabetized.

As an example:

import React from 'react';
import { connect } from 'react-redux';

import Foo from './Foo';

import './Bar.css';

This made sense to me, and would help a lot on several projects we've had lately.

The sort-imports rule looks like it can handle putting the import-for-side-effects after other imports, but doesn't at first glance support including the relative imports after absolute. We should investigate further.

[mikeselander]

Huge 👍 on this - I frequently get these slightly wrong manually and having a rule for this would prevent a lot of silly code churn.

[tfrommen]

Closing as done in #219.