Add nu (nushell) lexer support

[kdeelaka-superloop]

nu (nushell)
Nushell (or Nu) is a modern, cross-platform shell written in Rust that treats all data as structured, typed tables rather than raw text streams.

link here: https://www.nushell.sh/

Implementation in other libraries

• rust: https://github.com/nushell/nushell/tree/main/crates/nu-color-config/src