Add documentation on live-testing with E/App #850

	name: Lint JavaScript

	on:
	pull_request:
	types: [opened, synchronize]

	jobs:
	lint:
	runs-on: ubuntu-latest
	steps:
	- uses: actions/checkout@v2

	- uses: actions/cache@v2
	with:
	path: ~/.yarn
	key: ${{ runner.os }}-yarn-${{ hashFiles('**/yarn.lock') }}
	restore-keys: \|
	${{ runner.os }}-yarn-

	- name: Setup Node
	uses: actions/setup-node@v1
	with:
	node-version: "16.x"

	- name: Install node_modules
	run: yarn install --immutable

	- name: Verify there's no Prettier diff
	run: \|
	yarn lint --fix --quiet
	if ! git diff --name-only --exit-code; then
	# shellcheck disable=SC2016
	echo 'Error: Prettier diff detected! Please run `yarn lint --fix` and commit the changes.'
	exit 1
	fi

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