chore: Validating rules frontmatter on CI

[jeeyyy]

This PR does the below:

• Adds jest, for testing & assertions.
• Tests do the below:
  • checks if rules exist.
  • checks for existence of mandatory frontmatter attributes.
  • checks conditionally for existence of optional frontmatter attributes based on rule_type.
  • checks for all mandatory h2 headings.
  • checks for all mandatory h3 headings.
• Fixes all the rules markdown files, which were highlighted to have issues.
• Wired up CircleCI to catch validation errors on pull requests.

Closes issue:

• Validating rules format at build time #550

Updated

[WilcoFiers]

Much better. Thanks Jey!

[WilcoFiers]

Ahh bummer. Looks like this nesting describe doesn't work in Jest. :( Might as well put this into a single describe then.

[jeeyyy]

@WilcoFiers It does work, see: https://circleci.com/gh/act-rules/act-rules.github.io/1276?utm_campaign=vcs-integration-link&utm_medium=referral&utm_source=github-build-link