Initial idea for a front matter test

What does this MR do?

It would be helpful if the TW team could catch new documentation pages that were added to the repository sans front matter. (For those not on the team: we use front matter to track page ownership by stage and group.)

When I first created this MR, this merge request SHOULD have failed, because three new files had been added without frontmatter (list below). However, since this MR was created, these pages have since been fixed:

./development/integrations/codesandbox.md
./api/graphql/removed_items.md
./administration/integration/kroki.md

RESOLVED However, I've marked it as WIP because I'm getting a syntax error in the file:

scripts/lint-doc.sh: line 142: syntax error near unexpected token `fi'
scripts/lint-doc.sh: line 142: `fi'

Steps:

1. Fix the syntax error.
2. Ensure this new test works properly when results are found.
3. Ensure it also works properly when NO results are found (AKA all files have front matter)

Idea combined together from command-line suggestions on these pages.

• Finding files WITH frontmatter: https://leonid.shevtsov.me/post/find-files-that-have-yaml-frontmatter/
• Limiting the find to just markdown files: https://stackoverflow.com/questions/49553290/find-all-files-with-md-extension-and-execute-a-command-with-the-file-and-genera

Related issues

Closes #298761 (closed)

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