Back in 2018 someone asked whether Cargo planned to add support for installing 'ancillary files', such as manpages and data files, and got a resounding ¯\_(ツ)_/¯.
Has the situation changed at all in the seven years since? I am personally most interested in being able to install user-facing documentation for command line tools -- including but not necessarily limited to manpages -- but existing general-purpose build systems have a whole taxonomy of things you might want to install and where they should go.