[FEAT] Report version for niri WM

Description

When skimming the changelog, I noticed that support for version reporting at the WM level was handled as code changes within this project. For example in v2.46.0's changelog it mentions adding Hyprland's version.

I'm wondering if we can add the version for niri too.

Currently niri gets reported as WM: niri (Wayland) with v2.56.1.

Here's an example command showing how to obtain the version and its output:

$ niri --version
niri 25.11 (b35bcae)

Motivation

I use niri and sometimes when reporting bugs or feature requests reporting system details is helpful and having the version be included in the output would save time from running niri --version manually.

Additional context

No response