docs(openrpc): Use common crate for openrpc functionality

[oxarbitrage]

I created a common crate for openrpc functionality: https://github.com/zcash/openrpsee as the code is shared among the Z3 stack (Zaino, Zebra, Zallet).

Added @str4d as Co-author of the first commit: zcash/openrpsee@6482040

A similar PR exist for Zebra: ZcashFoundation/zebra#10201

[str4d]

Given that all of this code was authored by me and copied into the openrpsee crate, I would appreciate if my authorship credit was retained therein. Also note that copyright over my contributions to this crate is owned by ECC, not me.

[oxarbitrage]

Yea, sorry about that. This is something I need to ask you. My plan is to add LICENSE-APACHE and LICENSE-MIT into https://github.com/oxarbitrage/openrpsee and also squash the current commits (https://github.com/oxarbitrage/openrpsee/commits/main/) into one and add you as a Co-author of that initial commit.

Let me know if that will be enough or if you prefer something else. Thank you.

[oxarbitrage]

https://github.com/oxarbitrage/openrpsee/commits/main/

Let me know if that is good enough.

[oxarbitrage]

@str4d you are also welcome to give your feedback if any at zcash/openrpsee#1 for code location.

[oxarbitrage]

Rebased onto main and fixed a small typo in Cargo.toml where the comment said rpc.endpoint instead of rpc.discover.

[oxarbitrage]

@str4d rebased onto main and bumped openrpsee to 0.1.1. The new version includes crate metadata fixes (license, repository, description) that were needed for Zallet's Docker build to pass the cargo vet / supply-chain audit step. Everything is green now (NU7 Linux failure is repo-wide). Would appreciate a review when you get a chance.