swift-atomics required as a library dependency.

[wallysaurus]

import PackageDescription

let package = Package(
  name: "Scenes3D",
  products: [
    // Products define the executables and libraries a package produces, and make them visible to other packages.
    .library(
      name: "Scenes3D",
      type: .dynamic,
      targets: ["Scenes3D"]),
  ],
  dependencies: [
        .package(url: "https://github.com/apple/swift-atomics.git", from: "1.0.2")
    ],
  targets: [
    // Targets are the basic building blocks of a package. A target can define a module or a test suite.
    // Targets can depend on other targets in this package, and on products in packages this package depends on.
    .target(
      name: "Scenes3D",
      dependencies: [.product(name: "Atomics", package: "swift-atomics")]),
  ]
)
    ]
)