feat: function type

[DaniPopes]

Motivation

Closes #127

Solution

Adds a Function:

• a new-type in primitives (bytes24)
• an enum variant in dyn-abi type and value

and add parsing in sol-macro and sol-types

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[prestwich]

do we want impl Encodable<Function> for (Address, Selector) ?

[DaniPopes]

error[E0119]: conflicting implementations of trait `ty::Encodable<data_type::Function>` for type `(alloy_primitives::Address, [u8; 4])`
   --> crates/sol-types/src/types/data_type.rs:226:1
    |
219 | impl<T: Borrow<[u8; 24]>> Encodable<Function> for T {
    | --------------------------------------------------- first implementation here
...
226 | impl Encodable<Function> for (RustAddress, [u8; 4]) {
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ conflicting implementation for `(alloy_primitives::Address, [u8; 4])`
    |
    = note: upstream crates may add a new impl of trait `std::borrow::Borrow<[u8; 24]>` for type `(alloy_primitives::Address, [u8; 4])` in future versions