feat: prove that omega-regular languages are closed under left-concatenation by regular languages #398

	# taken from https://github.com/leanprover/lean4/blob/114f7e42f1abd10885e91698cd2910b1e4d76083/.github/workflows/pr-title.yml
	# the regex is altered to allow parentheses after the type as Mathlib does, e.g. `feat(CI): add workflow to check for commit convention`

	name: Check PR title for commit convention

	on:
	merge_group:
	pull_request:
	types: [opened, synchronize, reopened, edited]

	jobs:
	check-pr-title:
	runs-on: ubuntu-latest
	steps:
	- name: Check PR title
	uses: actions/github-script@v8
	with:
	script: \|
	const msg = context.payload.pull_request? context.payload.pull_request.title : context.payload.merge_group.head_commit.message;
	console.log(`Message: ${msg}`)
	if (!/^(feat\|fix\|doc\|style\|refactor\|test\|chore\|perf)($.$)?: .[^.]($\|\n\n)/.test(msg)) {
	core.setFailed('PR title does not follow the Commit Convention (https://leanprover.github.io/lean4/doc/dev/commit_convention.html).');
	}

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