is_variant

Generates methods to match enum variant.

Example

```rust use isvariantderive::IsVariant;

[derive(IsVariant)]

enum TestEnum { A, B(), C(i32, i32), D { _name: String, _age: i32 }, }

fn main() { let x = TestEnum::C(1, 2); assert!(x.is_c());

let x = TestEnum::A;
assert!(x.is_a());

let x = TestEnum::B();
assert!(x.is_b());

let x = TestEnum::D {_name: "Jane Doe".into(), _age: 30 };
assert!(x.is_d());

} ```