Backported Minecarts

-Rebuilt the mod from scratch because I lost the original source code.

-Backported minecart engine improvements, minecarts no longer derail and can now calculate the rails it will go through. This allows them to function past 48 minecartMaxSpeed without bugging out like crazy.

-Backported minecart rendering improvements on the client-side.

-This new version is in beta for one reason: The minecart rendering code is incredbily janky due to the old entity rendering code pre-1.21.2. For the most part, the minecarts render fine, but they occasionally stutter due to strange desyncs and what not.