feat: impl From<[(K, V); N]> for Map and Value

[paul-soporan]

This PR implements From<[(K, V); N]> for Map and Value, enabling things like:

let map = Map::from([("lorem", 40), ("ipsum", 2)]);

or

let v = [("lorem", 40), ("ipsum", 2)];
let x: Value = v.into();

Relevant PRs:

• Stabilize impl From<[(K, V); N]> for HashMap (and friends) rust-lang/rust#84111 implemented it for the collections in std
• Add IndexMap::from(array) and IndexSet::from(array) indexmap-rs/indexmap#205 implemented it for IndexMap

[martin-g]

The PR does not have any unit tests.

[paul-soporan]

I'm new to writing tests in Rust so I apologize if the answer is obvious:

From what I could find, it seems like this crate doesn't have any existing unit tests, but only integration tests and documentation tests.

The example I added to From<[(K, V); N]> for Value is already checked as a doc test, and I could add a doc test to the impl for Map too. Is there any advantage to writing unit tests instead (especially when all other From impls are only checked via doctests)?