Makes LineSelectionView available on macOS only

Author: simonbs

Sources/Runestone/TextView/Core/Mac/LineSelectionView.swift

@@ -1,3 +1,9 @@
-import Foundation
+#if os(macOS)
+import AppKit
 
-final class LineSelectionView: MultiPlatformView, ReusableView {}
+final class LineSelectionView: NSView, ReusableView {
+    override func hitTest(_ point: NSPoint) -> NSView? {
+        nil
+    }
+}
+#endif