Relax ToC requirement

[ParanoidUser]

Ahoy @sindresorhus 👋

Requiring an explicit Table of Contents (ToC) feels a bit outdated nowadays. Since 2021, GitHub has been automatically generating ToCs for all Markdown files, which is super handy. While I totally see the value in having a ToC, asking authors to add them manually can make their guides feel cluttered. It would be nice to keep things cleaner and let authors focus more on the content itself. I think we should relax this requirement - but I'd love to hear what others think.

Edit: If the community agrees with this proposal, I'd be happy to submit a PR to change it.