add building/decoding merkle path binary from/to merkle path json data

[shotasilagadzetaal]

Adding support for merkle path binary format.

[github-actions]

Congrats, you just opened your first pull request on libsv/go-bc! Thank you for contributing!

[sirdeggen]

I've built on top of this work in merkle-path-binary-format-interfaces, will raise another PR there. This isn't quite right just due to little endian-ness. See what you think over there, will raise once done suggesting things this evening.

[sirdeggen]

merged in another PR