Implement serialization via parity's scale codec

Ideally, this would be generic. Unfortunately, the generic API serde 
doesn't natively support borsh, nor SCALE, and while there is a serde 
SCALE crate, it's old. While it may be complete, it's not worth working 
with.

While we could still grab bincode, and a variety of other formats, it 
wasn't worth it to go custom and for Serai, we'll be using SCALE almost 
everywhere anyways.

substrate/tendermint/Cargo.toml

@@ -8,6 +8,8 @@ authors = ["Luke Parker <lukeparker5132@gmail.com>"]
 edition = "2021"
 
 [dependencies]
+parity-scale-codec = { version = "3.2", features = ["derive"] }
+
 async-recursion = "1.0"
 async-trait = "0.1"
 tokio = { version = "1", features = ["macros", "rt", "sync"] }