JsonSchema and lifetime

```rust
use nutype::nutype;
use serde::{Deserialize, Serialize};
use schemars::JsonSchema;

/// A valid user name.
#[nutype(
    derive(PartialEq, Eq, Debug, Serialize, Deserialize, JsonSchema)
)]
pub struct Username<'a>(&'a str);
```

appears to fail with

```
error: Deriving of trait `SchemarsJsonSchema` is not (yet) supported for an arbitrary type
```