v2.6.0

The most massive library grows by 5-15%.

• upgraded to c++20 (you'll have to change that otherwise it won't compile)
• engineer is officially dead
  • now we're using xmake
  • there was samurai too (ninja script generator) but that lasted like 3 days
• many small improvements
  • const arrays tr::Array<const T> and arrays of references tr::Array<T&> are now supported
  • tr::MaybePtr<T> is deprecated, now you can just do tr::Maybe<T&>
  • improved arenas with the new constructor using ArenaSettings for more settings and stuff
  • some other crap probably
  • i was gonna do more but it'd take too long