Create GH-ROBOTS.txt

[Wadeck]

I will discuss with Jonathan to ensure his bot will follow the org level instructions, otherwise it's either we block his bot completely or adding the instructions in all repo (latter is not really scalable)

Related to such PRs: https://github.com/jenkinsci/winstone/pull/246

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

Edit: Proposal made to Jonathan in a private channel.

[Wadeck]

Jonathan acknowledges the usage of the file. It seems he's checking that manually before running his bot.