doc: update PR checklist #824

	name: Elixir CI

	on: [pull_request]

	jobs:
	build:
	name: Build and test
	runs-on: ubuntu-20.04

	steps:
	- uses: actions/checkout@v2
	# cache the ASDF directory, using the values from .tool-versions
	- name: ASDF cache
	uses: actions/cache@v2
	with:
	path: ~/.asdf
	key: ${{ runner.os }}-asdf-v2-${{ hashFiles('.tool-versions') }}
	id: asdf-cache
	# only run `asdf install` if we didn't hit the cache
	- uses: asdf-vm/actions/install@v1
	if: steps.asdf-cache.outputs.cache-hit != 'true'
	# if we did hit the cache, set up the environment
	- name: Setup ASDF environment
	run: \|
	echo "ASDF_DIR=$HOME/.asdf" >> $GITHUB_ENV
	echo "ASDF_DATA_DIR=$HOME/.asdf" >> $GITHUB_ENV
	if: steps.asdf-cache.outputs.cache-hit == 'true'
	- name: Reshim ASDF
	run: \|
	echo "$ASDF_DIR/bin" >> $GITHUB_PATH
	echo "$ASDF_DIR/shims" >> $GITHUB_PATH
	$ASDF_DIR/bin/asdf reshim
	- name: Restore dependencies cache
	id: deps-cache
	uses: actions/cache@v2
	with:
	path: deps
	key: ${{ runner.os }}-mix-${{ hashFiles('**/mix.lock') }}
	restore-keys: ${{ runner.os }}-mix-
	- name: Install dependencies
	run: \|
	mix local.rebar --force
	mix local.hex --force
	mix deps.get
	- name: Compile (warnings as errors)
	run: mix compile --force --warnings-as-errors
	- name: Check formatting
	run: mix format --check-formatted
	- name: Run tests
	run: mix test
	- uses: mbta/actions/dialyzer@v1

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