Add more info to the vcs module

For Git, https://doc.qt.io/qbs/qml-qbsmodules-vcs.html#repoState-prop contains the latest commit. As this comment mentions, that is not enough. My use case is showing version info to the user for an application. Currently I can only show the commit SHA-1, whereas I really want to show the tag (e.g. v0.3.0), as that is what the user sees on the download page, not a SHA-1.

Alternatively, it would be good to have another example after this one that explains how to achieve this manually. I'm going to try out the code here and see if it works, but it would be good to have an official example in the docs for that.