Work on Nim 3 has begun

Relevant links:

Roadmap for 2025 and beyond - https://github.com/nim-lang/RFCs/issues/556

Nimony Architecture - https://github.com/nim-lang/nimony/blob/master/doc/design.md

Planned design - https://github.com/nim-lang/nimony/discussions/529

Nimony progress - https://forum.nim-lang.org/t/12693