Utility: disable DirectoryMonitor on Windows temporarily (#606)

This temporarily disables the functionality on Windows to match the
Linux port.  We should be able to reimplement this functionality as
already done in clang and swift-tools-support-core on Windows.

Author: compnerd

Sources/SwiftDocCUtilities/Utility/DirectoryMonitor.swift

@@ -11,7 +11,7 @@
 import Foundation
 import SwiftDocC
 
-#if !os(Linux) && !os(Android)
+#if !os(Linux) && !os(Android) && !os(Windows)
 import Darwin
 
 /// A throttle object to filter events that come too fast.