Update the generate.py script

[gpx1000]

• Add sample_hpp subcommand for generating Vulkan-Hpp samples with fallback to sample_api
• Automatically update Antora nav.adoc with new sample entries, nesting HPP variants under base samples
• Automatically add sample sections to category README with optional --readme-description flag
• Improve documentation with usage examples and optional parameter syntax
• Add slugify() helper to match CMake folder naming conventions

Description

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Fixes #

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Sample Checklist

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• I have tested the sample on at least one compliant Vulkan implementation
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• For new samples, I have added a tutorial README.md file to guide users through what they need to know to implement code using this feature. For example, see conditional_rendering
• For new samples, I have added a link to the Antora navigation so that the sample will be listed at the Vulkan documentation site

[asuessenbach]

It seems evaluating variables as part of a string should be done differently:

[asuessenbach]

You take "sample_api" as a fallback, but do not check for os.path.isdir?

[asuessenbach]

With my environment, cat_header now looks like "* xref::samples/{category}/README.adoc", which obviously is not found in the lines of nav.adoc.
What works for me is
cat_header = "* xref:samples/" + category + "/README.adoc"

And then, the entries generated in nav.adoc and README.adoc are a bit strange:
** {target_ref}[{nav_title}]
and

=== {target_ref}[{title}]

{desc}

[SaschaWillems]

How is this supposed to work? I don't see a hpp template file under "bldsys\cmake\template", where the other template files are placed.