Add Qt theme detection + Option

[capezotte]

Detects Qt widget style in LXQt, Trinity and, KDE Plasma, as well as GTK environments with Qt5ct. If they are the same as their GTK counterparts, display them as one entry.

Some caveats:

• I replaced the kde_theme environment variable with a togglable qt_theme environment variable. Should be fairly easy to add back in, though, if there is demand.
• Qt5ct stores fonts in a binary format. If portability is not an issue, the implementation contained in this pull request should be replaced with one using od --endian=big.

[hykilpikonna]

Thank you for your contribution!

This PR is merged into hyfetch since this repo (dylanaraps/neofetch) seems no longer maintained.

HyFetch is a fork of neofetch with LGBTQ pride flags, but the repo also maintains an updated version of the original neofetch, addressing many pull requests that are not merged in the original repo.

Read the "Running Updated Original Neofetch" section for more info!

[hykilpikonna]

Also just realized that this would set theme to ] when no themes are present...

[hykilpikonna]

Fixed