implement more detailed maintenance coverage tooling

the current maintainer chart at https://wiki.qt.io/Maintainers is not detailed enough for automated processing.
what we really want is a table that maps users to regular expressions identifying paths, qualified by the degree of responsibility (domain maintainer, domain co-maintainer, module maintainer, chief maintainer).
this can be used for automating various tasks, for example:

• adding relevant reviewers on gerrit
• assigning responsibilities for writing changelogs
• identifying areas which lack maintenance

there should be an online visualization. probably, that would look somewhat like a tree-based file manger which annotates the paths with names. if done right, this could be used to completely replace the maintainer chart.

the mapping table should be editable by self-service. it doesn't matter whether that would be an online service or a file in git.

the underlying account management (ideally, qt account) should track presence, so inactive accounts wouldn't falsify the results.