Add deserializeable test under feature

[jalil-salame]

Add a serde feature that allows you to specify the tests in a YAML/TOML file (e.g. from datatest):

[[test]]
value1 = "hello"
value2 = 1

[[test]]
value1 = "world!"
value2 = 2

#[derive(serde::Deserialize)]
struct TestCase {
    value1: String,
    value2: String,
}

// Would be executed with `TestCase{value1: "hello", value2: 1}` and `TestCase{value1: "world", value: 2}`
fn run_test(case: TestCase) {
    // ...
}

I would be interested in implementing this.