Add OpenFOAM v2406 to the supported versions

[MakisH]

@davidscn anywhere else we need to update this information in this repository?

Other than this, we should eventually update the tutorials:

• Quickstart: Update Quickstart for OpenFOAM v2406 and adapter v1.3.1 tutorials#545
• System tests defaults: actually, I think we should only update this once we generate new reference results. At the moment, we always need to specify each version separately.

The Foundation version branches are still not updated, but this is very low priority in my list. I will do another attempt maybe tonight/tomorrow, in the sake of the OpenFOAM Workshop this week. But this is independent of this PR.

TODO list:

• I updated the documentation in docs/
• I added a changelog entry in changelog-entries/ (create directory if missing)