NextJS 11.x

[haf]

This package is according to its dependencies forcing us to stay with NextJS 10 rather than being able to upgrade to v11.

It should be possible to upgrade to NextJS v11 without much breakage (looks fine in the browser, when I upgrade), but it needs to be tested and verified.

[smnh]

Updated nextjs peer dependency to >= 10.
Released sourcebit-target-next@0.6.4.