meson: docs: Add {html,man} targets, rename install-doc-*
We have toplevel html, man targets in the autoconf build as well. It'd be odd
to have an 'html' target but have the install target be 'install-doc-html',
thus rename the install targets to match.
Reviewed-by: Christoph Berg <myon@debian.org>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/
20231103163848.26egkh5qdgw3vmil@awork3.anarazel.de