Use title capitalization for page titles

[ggrossetie]

I would like to point out that the page titles now have inconsistent capitalization. Could we agree on a style and stick to it. See https://docs.asciidoctor.org/browser-extension/diagrams-extension-quickstart/ Notice "Extension Options" verse "Diagrams extension quickstart". In the core documentation, we tend to use title capitalization for page titles. See https://docs.asciidoctor.org/asciidoctor/latest/

Originally posted by @mojavelinux in #659 (comment)

[sturtison]

No problems, I can look at this quickly now.