RunOutput(launch:): rename parameter to ‘command’, add documentation.
RunOutput(launch:): rename parameter to ‘command’, add documentation.

Removed
```swift
	group.enter()
	defer {
		group.leave()
	}
```

because no matter what happens, "group.leave()" will be called when exiting this scope. As such it serves no purpose. We still need to use ‘group’ for the asynchronous reading of standard error though.

kareman/SwiftShell,kareman/SwiftShell,kareman/SwiftShell