defining first Display and Registry structs. Added Callback support for Registry.

examples/globals.rs

@@ -0,0 +1,26 @@
+// SPDIX-Licenes-Identifier: GPL-2.0-later
+
+use std::io;
+use wayland_client::display::Display;
+
+fn main() -> io::Result<()> {
+    let display = Display::new(None)?;
+    let mut registry = display.get_registry();
+
+    // define on_global callback 
+    registry.on_global(|interface, name, version|{
+        println!("interface: {interface}, version: {version}, name: {name}")
+    });
+    // define on_global_remove callback 
+    registry.on_global_remove(|_name| {
+        // left blank 
+    });
+    // register the callbacks in wayland 
+    registry.registry_listener();
+
+    // take a look around
+    let _ = display.roundtrip();
+
+    drop(display);
+    Ok(())
+}