[2023 day 14] Simple visualisation

Thought I'd share mine because most of the visualisations out there show the rocks sliding one cell at a time, all together. That looks nice but for my solution that's not how it works - I walk every row/col with two cursors.

Code here: https://github.com/sjmulder/aoc/blob/master/2023/c/day14.c

The visualisation is emitted right from the solution using a small library which dumps frames to ffmpeg.