we're using both `@url` and `@uref` commands in our documentation,
the overwhelming majority is `@uref`.
michael] ~/lilypond/Documentation/en (master)]> git grep '@url' | wc
-l
9
michael] ~/lilypond/Documentation/en (master)]> git grep '@uref' | wc
-l
622
The functionality is exactly the same:
https://www.gnu.org/software/texinfo/manual/texinfo/html_node/_0040url.html
I'd like to unify this. Shall we go with `@uref` to avoid big diffs
and because it is already the majority, or use `@url` what seems
more intuitive to me?