Implemented `setOutputType`.

set_output_type_implemented.swift

extension Publisher where Output == Never {
	func setOutputType<NewOutput>(to outputType: NewOutput.Type) /// (1) For the uninitiated, the `.Type`
	/// and `.self` suffixes here and at (2) refer to a metatype type and a type as a value,
	/// respectively. The language reference has a
	/// [solid section](https://docs.swift.org/swift-book/ReferenceManual/Types.html#ID455) on the topic.
		-> Publishers.Map<Self, NewOutput> {
		map { _ -> NewOutput in }
	}
}

Just("someString")
	.eraseToAnyPublisher()
	.ignoreOutput()
	.setOutputType(to: String.self) /// (2) Fixing downstream’s output type to `String`.
	.append("anotherStringPostFinished")