Some online documentation issues

[Ark-kun]

All hyperlinks on https://github.com/libvips/libvips/wiki/Nip2 are broken or incorrect.

https://github.com/libvips/nip2/wiki does not exist

https://www.libvips.org/ Documentation points to https://www.libvips.org/API/current/ which does not mention nip2.

Fortunately, the main https://github.com/libvips/nip2/README.md provides the answer:

Documentation: nip2 comes with a 50-page manual --- press F1 or Help / Contents in the program to view it.

I wish the nip2 documentation would be discoverable on https://www.libvips.org/ .