Show coordinates about lila-gif

[benediktwerner]

nice. still a bit hard to read with the grey color. but do you want to create a draft PR? would make a bit more sense to discuss stuff like this there than on the issue.

[cymruu]

I got it working to some point - there is still a lot of work to do with the antyaliasing to make the coordinates look nice and sharp. Sadly I have no idea how to improve it.
However I'm sharing my results with a hope it will be useful somehow.
Diff: https://github.com/lichess-org/lila-gif/compare/master...cymruu:lila-gif:cymruu/render-coordinates?expand=1
Branch: https://github.com/cymruu/lila-gif/tree/cymruu/render-coordinates

Images showing the results:
http://127.0.0.1:6175/image.gif?fen=4k3/6KP/8/8/8/8/7p/8

http://127.0.0.1:6175/image.gif?fen=4k3/6KP/8/8/8/8/7p/8&orientation=black

http://127.0.0.1:6175/example.gif

https://github.com/cymruu/lila-gif/blob/11b1386ae9f02d8660b7d0c17ad584300084fb79/example.gif

[cymruu]

I just realized it wasn't antyaliasing issue. Here are the updated version screenshots

http://127.0.0.1:6175/image.gif?fen=4k3/6KP/8/8/8/8/7p/8&orientation=black&lastMove=a1a2

http://127.0.0.1:6175/image.gif?fen=4k3/6KP/8/8/8/8/7p/8&lastMove=h1h2

http://127.0.0.1:6175/example.gif
https://github.com/cymruu/lila-gif/blob/c5fd03d08fe448eafc5da2baf8c9b3b782a2a247/example.gif?raw=true