DOC/CI: [PoC] surface doc preview in PRs
Proof of concept for 1./2. of https://github.com/pandas-dev/pandas/pull/52038#issuecomment-1481075756.
Here is what it looks like when [inspecting the job directly](https://github.com/pandas-dev/pandas/actions/runs/4500786499/jobs/7920364046?pr=52139#step:15:23):

![Screenshot from 2023-03-24 10-05-47](https://user-images.githubusercontent.com/6849766/227474845-7d394718-d1b4-4b21-84a4-c3a7d8522313.png)

And here is the same information as part of the [workflow summary](https://github.com/pandas-dev/pandas/actions/runs/4500786499?pr=52139):

![Screenshot from 2023-03-24 10-06-36](https://user-images.githubusercontent.com/6849766/227474873-446b70f7-50b7-4ce9-b66a-96e5af3df15f.png)

 Thanks @pmeier, this is interesting.  #52038 is not so much about how the link is shown to the users, but to publish the docs in a different server. It also has the approach of showing the link as a CI step in the main PR page. It's cool what you did here, but I think the link is still a bit hidden. But will leave this open while we still check if #52038 works for us, as having the link as the CI summary is cool even if we have other methods to show it, and if we stay with the old approach it can make sense to merge this. > about how the link is shown to the users, but to publish the docs in a different server

Ok, in that case this PR is not the right way. Feel free to close.

> It also has the approach of showing the link as a CI step in the main PR page.

What is the "main page" here? If you mean that it is displayed as an individual step in the job, this can be trivially achieved here as well. Taking this a step further, it is also not hard to get a bot to comment on the PR with a link to the preview as soon as it is uploaded for maximum visibility. The main PR page would be for example: https://github.com/pandas-dev/pandas/pull/52139

What you implemented requires to go to the actions page for the PR. I'll close this one for now, but feel free to reopen, suggest changes or implement a new PR once the outcome of #52038 is clear. Thanks! Sorry, I still don't understand what you mean. How do you want to put anything in the PR thread except for having a bot or the like add a comment? Maybe I'm missing the big picture in #52038, but so far I fail to see how it would solve this as well. We already have an action to write a comment with the preview link when a comment with the content `/preview` is created. The new option we're exploring is to create the link in the list of CI builds (where we see the result of each individual build). Ok, got it now. Thanks for the explanation!