DOC: Add note to docs on DataTree root-group naming conventions

[kmuehlbauer]

root group name is always "/"

• Closes Losing top level name attribute when saving and then reopening using h5netcdf #9293
• User visible changes (including notable bug fixes) are documented in whats-new.rst

[flamingbear]

I played with the generated doc strings but couldn't get them to work with the .. note:: pragma But have added what I would suggest and shown some output.

You can apply these suggestions and merge this or I can just pull these changes into the #9033.

[kmuehlbauer]

You can apply these suggestions and merge this or I can just pull these changes into the #9033.

Oh well, I've just applied the proposed changes. But do whatever suits best for your doc integration workflow. You might still pull everything you need from here. I can also squash everything into one commit, if that's easier.

[flamingbear]

@kmuehlbauer I think this is fine to merge or close either way is fine with me. I grabbed the pieces you wrote trying to test it out. ec341ad But that may still take a while to get to main. I'll approve this for you in either case.

[flamingbear]

Looks good, thanks for the update.

[kmuehlbauer]

OK, then let's merge it here to closeout #9293.