Add support for F16-F24 (#641)

* Added support for F16-F19 keys.

* Documented support for F16-F19 keys

* Added support for F20 key

* Added support for F21-F24 on platforms except macOs

* Added support for F21-F24 on macOs

* Documented addition of F16-F24 keys

* Added missing ref qualifier

* Fixed compilation error on 1.24.1

* Refactored methods in macOs events_loop and view files

src/events.rs

@@ -317,6 +317,15 @@ pub enum VirtualKeyCode {
     F13,
     F14,
     F15,
+    F16,
+    F17,
+    F18,
+    F19,
+    F20,
+    F21,
+    F22,
+    F23,
+    F24,
 
     /// Print Screen/SysRq.
     Snapshot,