Antora build errors

[oddhack]

Noticed a couple of dozen asciidoctor errors while building the tutorial component of the docs site, see https://github.com/KhronosGroup/Vulkan-Site/actions/runs/19908462242/job/57849207297 . Looks like minor markup stuff, mostly 'target of xref not found' and a couple of 'level 0 sections can only be used when doctype is book'.

[SaschaWillems]

All the tutorial errors all seem to be related to the recently merged simple game engine chapters done by @gpx1000, so prob. something Steven should look into.

Maybe a good idea to exclude them until that part of the tutorial is actually finished?

[gpx1000]

Yep looking into it