Completely rewrites xterm-colortest
Completely rewrites xterm-colortest

Only prints the list of hex codes for the set of colors.
- Pipe to something for it to be useful, e.g.:
    ```sh
    xterm-colortest \
    | xargs -iZ convert -size 10x10 xc:Z miff:- \
    | montage -mode concatenate - x:
    ```

Set colors via env var (`$COLORS`).
- only supports 88 / 256

benizi/dotfiles,nestukh/dotfiles,benizi/dotfiles,nestukh/dotfiles,benizi/dotfiles,benizi/dotfiles,benizi/dotfiles,nestukh/dotfiles,benizi/dotfiles,nestukh/dotfiles,nestukh/dotfiles,benizi/dotfiles,nestukh/dotfiles,nestukh/dotfiles,nestukh/dotfiles,benizi/dotfiles