v5.3 release - horizontal springs!

First update on pico-sonic since the release!

I added horizontal springs matching the original game. They can be annoying at times, but sometimes hint beginner players at hidden location located behind them…

I also simplified the code (removed hacks required in early prototyping), which modified slope physics a little on steep slopes, but nothing too noticeable. I need to remove some code to add new features instead anyway, due to PICO-8 limitations (despite using a hacked version of PICO-8 I still follow the ultimate cartridge file size limit).

Enjoy!