Add time_and_date plugin. Use it for timezones and date formats around the bot.

backend/src/utils/isValidTimezone.ts

@@ -0,0 +1,7 @@
+import moment from "moment-timezone";
+
+const validTimezones = moment.tz.names();
+
+export function isValidTimezone(input: string) {
+  return validTimezones.includes(input);
+}