[Documentation] Stable docs are still on v0.2.4

[leburgel]

There seems to be an issue with the stable docs, which haven't been updated to a new version since v0.2.4 for some reason. I noticed when trying to use the stable version with DocumenterInterLinks, which doesn't work because v0.2.4 was still built with Documenter v0.

[leburgel]

So it seems like just none of the actions are triggering on the releases since v0.2.4, and I have no clue why. I can manually trigger CI on a tag though, so if all else fails we can add a workflow_dispatch trigger to the documentation action so that we can trigger it manually on the most recent version so that it at least shows up as the stable docs page.

[lkdvos]

I think I managed to fix this, it seems there was a missing documenter_key secret somewhere. I at least added the latest version, but in principle we should run the action for the previous versions as well, if we think this is important?

[leburgel]

I don't think the previous versions are that important, as long as it updates systematically from now on. I'm still confused why this one needed an actual ssh key while all the other repos seem to be fine with just the github token in the documenter action. Anyway, solved is solved.