Upgrade to Box2D v3

[duffn]

Thanks for the great template.

It would be nice to update to Box2D v3 as v2 will not be updated any longer.

• v3 background: https://box2d.org/posts/2023/01/starting-box2d-3.0/
• Migration guide: https://box2d.org/documentation/md_migration.html

[tupini07]

hi! thanks a lot for the comment. I was playing with this a bit in a new branch but I'm getting a segmentation fault when the player box collides with a 'floor box', and I'm not sure what to make of it.

I might come back to this in the coming days but first I think I'll need to read up a bit more on it to better understand what's going on 😄