Since we don't want to add too many dependencies for now, use our own small hexdump lib `hexhex` instead of `hexyl`.
* implemented 3 tests * valid opcodes * invalid opcodes * header too short * fixed byteorder and bit shifting for flags * added hexdump for main function for testing purposes
Co-authored-by: ddidderr <ddidderr@paul.network> Reviewed-on: #12
