Unary tuple struct getter/setter

[Jasha10]

Currently getset seems to work with ordinary structs but not with tuple structs:

#[derive(getset::Getters)]
pub struct MyType(u64);

 1  error: Expected the field to have a name
    --> crates/entities/src/newtypes.rs:265:39
     |
 265 | pub struct NonNegativeTimeDeltaMicros(u64);

The following also fails:

#[derive(getset::Getters)]
pub struct MyType(#[getset(get)] u64);

Pitch

It would be convenient to derive get, set, etc for unary tuple structs.
This naming convention has precedent in the standard library. For example, we have std::num::NonZeroU64::get which returns the u64 type that is wrapped by the NonZeroU64 tuple struct.