Update build matrix to Node 20.x and 21.x #516

	on: [push]
	name: build
	jobs:
	build:
	runs-on: ubuntu-latest

	strategy:
	matrix:
	node: ["20.x", "21.x"]

	name: Node.js ${{ matrix.node }}
	steps:
	- uses: actions/checkout@v4

	- name: Set up Node.js ${{ matrix.node }}
	uses: actions/setup-node@v4
	with:
	node-version: ${{ matrix.node }}

	- name: Install dependencies
	run: \|
	npm ci
	node ./node_modules/elm/install.js

	- name: Audit signatures
	run: npm audit signatures

	- name: Generate intermediate files
	run: \|
	# By compiling both `Main.elm` and `Worker.elm`, we make sure all
	# intermediate files are present before the next steps run.
	#
	# Otherwise, parcel would compile both files in parallel which can
	# lead to data races and let one of the compiler processes fail with
	# an error about corrupt files.
	npx elm make app/elm/Main.elm --output /dev/null
	npx elm make app/elm/Worker.elm --output /dev/null

	- name: Run tests
	run: npm test

	- name: Build assets
	run: npm run prod

	- name: Check formatting
	run: \|
	npx elm-format --validate app/elm tests
	npx prettier --check "app/js/*.js"

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