relnotes template: some additions

Bring some tweaks from the 14.0 release notes into the template.

• Deprecated/removed drivers subsection
• Documentation section + man-pages subsection
• Links to supported hardware and platforms in Hardware Support section

Reviewed by: carlavilla, emaste, karels
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D42571