Adding this module as a dependency, Tokamak users would only need to add a single import regardless of the platform they're targeting. Thus, instead of
```swift
#if canImport(SwiftUI)
import SwiftUI
#else
import TokamakDOM
#endif
```
a single `import TokamakShim` is enough. `TokamakShim` re-exports correct modules based on a target platform.
I've also renamed the `TokamakDemo Native` directory to `NativeDemo` for brevity.
`xcodebuild` output in the `macos_demo_build` job is now passed to `xcpretty` for more readable build logs.
Jed Fox