ci: Add markdownlint, test_html_build, and build_docs workflows #2

	---
	# yamllint disable rule:line-length
	name: Markdown Lint
	on: # yamllint disable-line rule:truthy
	pull_request:
	merge_group:
	branches:
	- main
	types:
	- checks_requested
	push:
	branches:
	- main
	workflow_dispatch:
	permissions:
	contents: read
	jobs:
	markdownlint:
	runs-on: ubuntu-latest
	steps:
	- name: Update pip, git
	run: \|
	set -euxo pipefail
	sudo apt update
	sudo apt install -y git

	- name: Check out code
	uses: actions/checkout@v3

	- name: Lint README.md
	uses: docker://avtodev/markdown-lint:master
	with:
	args: README.md
	config: .markdownlint.yaml

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