Set up linting for GitHub Actions workflows

[Belco90]

What internal change would you like to have?

Set up actionlint in the repo.

What problem will this change solve?

Anticipate mistakes when writing GitHub Actions workflows.

Do you want to help make the feature?

Yes

Is there anything else we need to know?

No response

[HonkingGoose]

Maybe this VSCode extension can help with writing/checking GitHub Action files:

https://marketplace.visualstudio.com/items?itemName=github.vscode-github-actions

[Belco90]

That will definitely help (I use a similar one for my IDE), but would be better to lint it in CI to make sure it's fine no matter the developer local config.

[HonkingGoose]

Linting in CI is best! 😄