Kernel: Add key_code_count

Author: https://github.com/willmcpherson2
Commit: 61a6ae038e
Pull-request: https://github.com/SerenityOS/serenity/pull/1150
Reviewed-by: https://github.com/awesomekling
Reviewed-by: https://github.com/bugaevc

Kernel/KeyCode.h

@@ -138,6 +138,7 @@ enum KeyCode : u8 {
 
     Key_Shift = Key_LeftShift,
 };
+const int key_code_count = Key_Logo;
 
 enum KeyModifier {
     Mod_None = 0x00,