Attribute macro for less verbose creation of enums having different types as variants.

Also automatically implements From, TryFrom and fn is<T>() -> bool to check if its inner item is of type T .

Usage:

```rs struct A; struct B; struct C;

[tyenum]

enum Test { A, BB(B), C(C), } ```

results in:

```rs enum Test { A(A), BB(B), C(C), }

impl Test { fn is>(&self) -> bool { T::istypeof(self) } } ```

and for every variant (in this example A):

```rs impl From for Test { fn from(variant: A) -> Self { Test::A(variant) } }