zig data structures

This is a compilation of common data structures and trees in Zig. Most of these exist in the Rust ecosystem already (not standardised), so I'm mostly porting them over.

It's a work in progress, with plans for:

bitmap
merkle tree
merkle mountain range (mmr)
sparse merkle tree (smt)
lamport clock
vector clock

Note: I just started writing Zig, so don't expect things to necessarily work as expected.