LibChess: Add the UCI quit command

Author: https://github.com/tcl3
Commit: 13dbc69c23
Pull-request: https://github.com/SerenityOS/serenity/pull/18140
Issue: https://github.com/SerenityOS/serenity/issues/17427
Reviewed-by: https://github.com/LucasChollet
Reviewed-by: https://github.com/petelliott

Userland/Libraries/LibChess/UCICommand.cpp

@@ -333,4 +333,17 @@ DeprecatedString InfoCommand::to_deprecated_string() const
     return "info";
 }
 
+QuitCommand QuitCommand::from_string([[maybe_unused]] StringView command)
+{
+    auto tokens = command.split_view(' ');
+    VERIFY(tokens[0] == "quit");
+    VERIFY(tokens.size() == 1);
+    return QuitCommand();
+}
+
+DeprecatedString QuitCommand::to_deprecated_string() const
+{
+    return "quit\n";
+}
+
 }