Stabilize `+csp`

[brillout]

Description

See http://vike.dev/csp.

It's currently a beta feature. Let's see if there are issues with it. If no users complain, let's consider it a stable feature.

[PheysX]

Amazing work. Do you have a timetable for the next release? @brillout

[brillout]

No but you can use the pre-release, see #1554 (comment).

[PheysX]

Works like a charm in my tests ❤️