Tentative workflow improvement
This improves the workflow of the doc-builder bot by adding a single comment when the PR is opened.

When the PR is closed or merged, it edits that comment. If the PR is reopened, it re-edits that comment.
_The documentation is not available anymore as the PR was closed or merged._<|||||>See the edits of the comment above.<|||||>I'm ok with both solutions 1 and 3 - I agree that it might be odd for the comment to be deleted, and hiding the comment removes that peculiarity.

If it's ok with you, I'll merge this PR as it is, as it is already an improvement of the workflow. I'm very open to any PR you offer regarding 1 or 3.<|||||>**Seems it works again**

off topic - but today when I checked the link, I always get 
```
404

Sorry, we can’t find the page you are looking for.
```

Yesterday, I saw it worked. (Maybe @LysandreJik you are already aware of this fact?)<|||||>Hey @ydshieh, I believe these are due to errors on our backend; we're currently setting up a system that would make for a better way to share that info with the contributors. In the meantime, please do not hesitate to ping us on the PRs themselves with the commit that failed to be deployed. Thank you!