* create hash submodule for block
* create header submodule for block
* create serialize submodule for block
* add newline to hash.rs (fmt)
* Update zebra-chain/src/block/tests.rs
Co-authored-by: Jane Lusby <jlusby42@gmail.com>
Co-authored-by: Henry de Valence <hdevalence@hdevalence.ca>
Co-authored-by: Jane Lusby <jlusby42@gmail.com>