Add a default language selection button

[bastienrobert]

I use the Feature request template from sanity-io/sanity.

Is your feature request related to a problem? Please describe.

During the contribution, it would be useful to be able to select a language to be displayed by default in the panes.

Describe the solution you'd like

I think a simple selection button in the navbar would be sufficient. Unfortunately it seems that this is not possible today.

Describe alternatives you've considered

An alternative could be to add a button in the top of a pane, but this would only work on panels containing repeatable document types and not on singletons:

Additional context

This request is directly linked to sanity-io/sanity, it should be moved if it seems interesting in this particular situation.

[vincentboiardt]

It would also be useful if this could be used so that it's possible to create documents in one language (eg "Swedish") without the document existing in the base language (eg "English").

[jclusso]

Is there any way to do what @vincentboiardt has mentioned?