Remove clipboard_windows and simplify modules

src/platform/macos.rs

@@ -0,0 +1,16 @@
+use crate::ClipboardProvider;
+
+use raw_window_handle::HasRawWindowHandle;
+use std::error::Error;
+
+pub fn new_clipboard<W: HasRawWindowHandle>(
+    _window: &W,
+) -> Result<Box<dyn ClipboardProvider>, Box<dyn Error>> {
+    Ok(Box::new(clipboard_macos::Clipboard::new()?))
+}
+
+impl ClipboardProvider for clipboard_macos::Clipboard {
+    fn read(&self) -> Result<String, Box<dyn Error>> {
+        self.read()
+    }
+}