Simplify platform-specific keyboard layouts with Accel key and global platform variable (#748)

* Simplify platform-specific keyboard layouts with Accel key and global platform variable


Co-authored-by: Dennis <dennis@kobert.dev>

editor/src/messages/globals/globals_message_handler.rs

@@ -0,0 +1,18 @@
+use crate::messages::prelude::*;
+
+#[derive(Debug, Default)]
+pub struct GlobalsMessageHandler {}
+
+impl MessageHandler<GlobalsMessage, ()> for GlobalsMessageHandler {
+	#[remain::check]
+	fn process_message(&mut self, message: GlobalsMessage, _data: (), _responses: &mut VecDeque<Message>) {
+		match message {
+			GlobalsMessage::SetPlatform { platform } => {
+				GLOBAL_PLATFORM.set(platform).expect("Failed to set GLOBAL_PLATFORM");
+			}
+		}
+	}
+
+	advertise_actions!(GlobalsMessageDiscriminant;
+	);
+}