expose building documentation for user modules not in the Sage library #6389
Description
It would be neat to be able to do:
sage -docbuild foo.py
for a single file not in the library.
See also:
CC: @mkoeppe @jdemeyer @vbraun @fchapoton @williamstein @dimpase @nthiery @hivert @embray
Component: documentation
Keywords: sphinx
Issue created by migration from https://trac.sagemath.org/ticket/6389