✨ Features

- Implement `BFieldCodec` for `u8` and `u16` (8ec5f680)
- Add conversions from and to `BFieldElement` (8e403080)
- Easily construct polynomials `x^n` (2c1c08d8)
- Generalize polynomial multiplication (4235a802)

♻️ Refactor

- *(polynomial)* Disallow negative exponents (5f81f862)
- (!) *(polynomial)* Generalize `evaluate()` (8482f939)
- (!) Move canon check to `BFieldElement` (7dafa32e)