An implementation of 'Sparse Merkle Tree' with versioned features.
```rust type Smt = xsmt::VsSmt>; let smt = Smt::default(); ...
type Smt = xsmt::VsSmt2, Vec>; let smt = Smt::default(); ... ```
SEE ALSO: - VSDB, a database with powerful version management capabilities - sparsemerkletree, the original upstream crate