iglass 1.5.0: niri, GNOME 51 and your distro

Added

• niri and GNOME 51 blur. niri 26.04+ and GNOME 51+ blur behind apps that ask for it, which
  kitty does from 0.46.2 and Ghostty from 1.4. iglass recognizes the desktop and its version and
  picks Frosted where the glass is blurred, Tinted where it isn't. On niri, with a terminal that
  doesn't ask yet, it prints the window rule that adds blur.
• Distributions are recognized: Arch-based systems (Garuda, CachyOS, Manjaro, EndeavourOS),
  Debian and Ubuntu, Fedora, and openSUSE get install hints for their own package manager, in
  iglass and in the install script.
• doctor shows the desktop and its version next to the distribution, and says per terminal
  whether the desktop blurs behind it.

Fixed

• On Ubuntu (XDG_CURRENT_DESKTOP=ubuntu:GNOME) messages named the desktop "ubuntu"; they now say
  GNOME, and KDE is called KDE Plasma.