`latest` and `stable` versions in the docs

[MatteoRobbiati]

Hi all,

we want to have both the two cited versions in the documentation page. If RTD's standard theme provided this feature by default, we cannot say the same about furo. Therefore, as discussed earlier with @AleCandido we will probably have to work from the point of view of workflows.

One strategy might be to compile the documentations separately and trigger the workflow at the time branch and tag are updated to recompile latest and stable, respectively.

[alecandido]

Just to write also here:

• [ ] the RTD theme was not providing the version picker (the box in the bottom-left corner), it is an integration added by the RTD website while compiling it - irrespectively of the theme used, we have to implement it ourselves (but restricting to the latest and stable only should be simple)
• [ ] we do not want to touch too much the docs, at the moment, so the picker will be in the website, while the docs versions will just be deployed on different sub-urls (/latest/ and /stable/)
• [ ] latest will be simply updated by every push on master
• [ ] stable we interpret as the last tag, but we should still say what last means, options:
  • chronologically sorted: last one published replace stable (we'll start from here because it's the simplest)
  • semver sorted
  • semver sorted, excluding pre-releases

The moment we will move from iframes to embedded docs we can consider more complex features (like making the picker available on the docs page itself, that will be also a website page)