Link Varnish X-Key broken

[art-cg]

In the Cache-Documentaion there is a broken link to X-Key.
https://github.com/dunglas/vulcain/blob/main/docs/cache.md

Broken in Master-Branch
https://github.com/varnish/varnish-modules/blob/master/docs/vmod_xkey.rst

Branch 6.5 is available
https://github.com/varnish/varnish-modules/blob/6.5/docs/vmod_xkey.rst

[andrerom]

Generated docs have been removed in master, seems only place to link to is now: https://github.com/varnish/varnish-modules/blob/varnish-modules-0.18.0/src/vmod_xkey.vcc.

Here example link with tag to avoid link breaks, but could be master too, same file there.