• Fixes sixel preview writes out of bounds #1765

This PR provides built-in support for sixel images, which are detected when reading the contents of a file for previewing purposes. Multiple sixel images can be displayed alongside with text if output by the previewer script.

Example previewer script:

#!/bin/sh

width=$(($2 / 2))
height=$(($3 / 2))

chafa -f sixel -s "${width}x${height}" --animate off -t 1 --bg black "$1"
stat "$1" | bat --tabs 4 --terminal-width "$2" --color=always
chafa -f sixel -s "${width}x${height}" --animate off -t 1 --bg black "$1"

Apparently --polite on is no longer needed because this new implementation does not require the first two bytes of the previewer output to be the sixel header (ESC + P), but I think it is still better to include it in the wiki as a recommendation.