Fix doc since marker files are dotfiles

[hashar]

The documentation for the marker files missed the leading dot.

They were introduced by #1016.

Testing done

Submitter checklist

• Make sure you are opening from a topic/feature/bugfix branch (right side) and not your main branch!
• Ensure that the pull request title represents the desired changelog entry
• Please describe what you did
• Link to relevant issues in GitHub or Jira
• Link to relevant pull requests, esp. upstream and downstream changes
• Ensure you have provided tests - that demonstrates feature works or fixes the issue

[timja]

Oops thanks!

I assume I copy pasted and the . got dropped by a word boundary thing.

[hashar]

I assume I copy pasted and the . got dropped by a word boundary thing.

I guess so yes. Thank you very much for the documentation you wrote in #1016 that has let me setup and enforce ESLint for a plugin :]