Revamp key/code input processing which fixes Option key on Mac and other locales

Closes #742
Closes #746

frontend/src/utility-functions/platform.ts

@@ -49,6 +49,6 @@ export function operatingSystem(detailed = false): string {
 	return osTable[userAgentOS || "Unknown"];
 }
 
-export function operatingSystemIsMac(): boolean {
+export function platformIsMac(): boolean {
 	return operatingSystem() === "Mac";
 }