docs: add CONTRIBUTING.md with development and PR workflow guide (#389) #2791

	name: fourmolu
	on: push
	jobs:
	format:
	runs-on: blacksmith-4vcpu-ubuntu-2404
	steps:
	- uses: actions/checkout@v6
	with:
	token: ${{ secrets.GITHUB_TOKEN }}

	- name: Cache fourmolu
	id: cache-fourmolu
	uses: actions/cache@v5
	with:
	path: ~/.local/bin/fourmolu
	key: fourmolu-0.19.0.0

	- name: Install fourmolu
	if: steps.cache-fourmolu.outputs.cache-hit != 'true'
	run: \|
	mkdir -p ~/.local/bin
	curl -sL https://github.com/fourmolu/fourmolu/releases/download/v0.19.0.0/fourmolu-0.19.0.0-linux-x86_64 -o ~/.local/bin/fourmolu
	chmod +x ~/.local/bin/fourmolu

	- name: Add fourmolu to PATH
	run: echo "$HOME/.local/bin" >> $GITHUB_PATH

	- name: Format code
	run: make fmt

	- name: Commit formatted code
	run: \|
	git config --local user.email "github-actions[bot]@users.noreply.github.com"
	git config --local user.name "github-actions[bot]"
	git add -A
	git diff --staged --quiet \|\| git commit -m "Auto-format code with fourmolu"

	- name: Push changes
	uses: ad-m/github-push-action@master
	with:
	github_token: ${{ secrets.GITHUB_TOKEN }}
	branch: ${{ github.ref }}

Provide feedback