Fix Regex to allow Umlaute "üÜ" in username (#1466)

## Description:

Modified the regex pattern & full unicode support (/u)

1) Allow Umlaute "üÜ" in usernames on client-side
2) Allow Umlaute "üÜ" in usernames on server-side

Before only the name "üÜüÜ" would have been possible as the pattern was
|üÜ -> or "üÜ" as a combined sequence
|[üÜ] -> or either one of these letters



## Please complete the following:

- [x] I have added screenshots for all UI updates
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file
- [x] I have added relevant tests to the test directory
- [ ] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced
- [x] I have read and accepted the CLA aggreement (only required once).

Not 100% sure what/where else to test. I started couple of private
lobbies with various names.

## Please put your Discord username so you can be contacted if a bug or
regression is found:

[UN nvm]

src/core/Schemas.ts

@@ -162,7 +162,7 @@ export const TeamSchema = z.string();
 const SafeString = z
   .string()
   .regex(
-    /^([a-zA-Z0-9\s.,!?@#$%&*()\-_+=[\]{}|;:"'/\u00a9|\u00ae|[\u2000-\u3300]|\ud83c[\ud000-\udfff]|\ud83d[\ud000-\udfff]|\ud83e[\ud000-\udfff]|üÜ])*$/,
+    /^([a-zA-Z0-9\s.,!?@#$%&*()\-_+=[\]{}|;:"'/\u00a9|\u00ae|[\u2000-\u3300]|\ud83c[\ud000-\udfff]|\ud83d[\ud000-\udfff]|\ud83e[\ud000-\udfff]|[üÜ])*$/u,
   )
   .max(1000);