Update CODEOWNERS to include navigation

[osdnk]

After recent problems with navigation,e g.,

• non-consistent sheets with swap aggregator (android)
• last minute problems on profiles

and the general observation that a lot of changes are quite nonsense here (e.g., some presents clearly doing nothing, because they should be used for a different type of navigator) I hope this is a good idea to have at least temporarily some lock over those files.

I talked with @jinchung and she shares my understanding. Additionally, this is a good indicator we need to have a knowledge about the navigation better distributed