Turnstile: require token before joining a multiplayer game (#2572)

When user tries to join either a public or private multiplayer game, the
turnstile callback is triggered, and the turnstile token is passed to
the server when joining a game.

## 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
- [x] I confirm I have thoroughly tested these changes and take full
responsibility for any bugs introduced

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

evan

src/client/ClientGameRunner.ts

@@ -58,6 +58,7 @@ export interface LobbyConfig {
   clientID: ClientID;
   gameID: GameID;
   token: string;
+  turnstileToken: string | null;
   // GameStartInfo only exists when playing a singleplayer game.
   gameStartInfo?: GameStartInfo;
   // GameRecord exists when replaying an archived game.