Small command-line application to view images from the terminal
written in Rust. It uses lower half blocks (\u2584) to fit 2 pixels
into a single cell by adjusting foreground and background colours
accordingly.

When run, viu will check the value of $COLORTERM. If it contains
either truecolor or 24bit, truecolor (16 million colors) will be
used. If not, it will fallback to using only ansi256.