Use Singularity 3.8.1, from https://github.com/singularityhub/github-… #17

	# Check that there is correct markdown in all files
	name: Check markdown

	# Check spelling on the 21st day of the month.
	# 21st as the first letter of this repo is the 21st letter in the alphabet.
	on:
	push:
	pull_request:
	schedule:
	- cron: "0 0 21 * *"

	jobs:
	check_markdown:

	runs-on: ubuntu-latest
	env:
	GITHUB_PAT: ${{ secrets.GITHUB_TOKEN }}
	steps:

	- name: Set up Git repository
	uses: actions/checkout@v4

	- uses: articulate/actions-markdownlint@v1
	with:
	config: .markdownlint.jsonc
	ignore: .markdownlintignore

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