Suppress clippy lint for atomics

[rust1248]

When I try to use this crate on a struct with atomics, clippy complains about the following:

warning: a `const` item should never be interior mutable
  --> src/main.rs:14:5
   |
14 | /     const DEFAULT: Self = Self {
15 | |         atomic: <AtomicUsize as ::const_default::ConstDefault>::DEFAULT,
16 | |     };
   | |______^
   |
   = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#declare_interior_mutable_const
   = note: `#[warn(clippy::declare_interior_mutable_const)]` on by default

This is the code I used:

use std::sync::atomic::AtomicUsize;

static T: Test = <Test as const_default::ConstDefault>::DEFAULT;

#[derive(Debug)]
struct Test {
    atomic: AtomicUsize,
}

impl ::const_default::ConstDefault for Test
where
    AtomicUsize: ::const_default::ConstDefault,
{
    const DEFAULT: Self = Self {
        atomic: <AtomicUsize as ::const_default::ConstDefault>::DEFAULT,
    };
}

fn main() {
    dbg!(&T);
}

I think the crate should add a #[allow(clippy::declare_interior_mutable_const)] above const DEFAULT: Self = Self {, so that it stops complaining

I can open a PR if you are interested