Consider adding the readthedocs preview for PRs

[ekouts]

More information here: https://docs.readthedocs.io/en/stable/pull-requests.html#preview-documentation-from-pull-requests

All we need to do is to set Build pull requests for this project in the advanced settings of the rtd project: https://docs.readthedocs.io/en/stable/guides/pull-requests.html

[vkarak]

I have enabled the rtd webhook to run also on pull requests; let's see it is going to trigger the build in the next PR.