Add '--version' option

[EpicWink]

Add a --version application option which simply shows the version of microdnf, then exits with status 0.

This makes the solution in #135 (comment) work when microdnf is actually being used, and allows users to verify dnf is working easily in a cross-compatible way.

A simple implementation could delegate to dnf repoquery --installed microdnf.

[m-blaha]

Hello, thank you for reaching out to us!

Our development team is currently prioritizing work on dnf5, which has already replaced microdnf in Fedora. Given this focus, this particular issue may not receive immediate attention in our current roadmap.

However, we would be very happy to review any pull requests you or others might be interested in submitting.