Saturn SDK v2

[arrudagates]

Saturn SDK v2 will be a complete rewrite on Rust using Subxt as the Substrate client, the goal is to have a WASM binary with TypeScript interfaces generated through bindgen, this should solve every issue that comes with p.js api's approach of type generation by using only Rust primitives with direct TS equivalents in the function signatures and letting the Rust/Substrate type conversions happen inside the Rust functions.

As a bonus we also get a Rust version of the SDK with no extra work.