Antora ci

[gpx1000]

Description

This adds building the antora documentation to the CI for Vulkan Samples. This way we can capture any problems with the future changes to tutorials that are automatically harvested in creating the vulkan documentation site.

Fixes #1040 https://github.com/KhronosGroup/Vulkan-Site/issues/82

NB: to see example of the build here: https://gpx1000.github.io/Vulkan-Samples/samples/latest/README.html When this is merged, the build job should publish to here:
Note that to make this work, need to change the settings for the repo to publish form the gh-pages branch. https://khronosgroup.github.io/Vulkan-Samples/samples/latest/README.html