Reduce amount of copies for HashedString for improved performance

Signed-off-by: Deukhoofd <deukhoofd@gmail.com>

src/Parser/Lexer.cpp

@@ -256,7 +256,7 @@ namespace Porygon::Parser {
             case HashedString::ConstHash("while"):
                 return new SimpleToken(TokenKind::WhileKeyword, start, 5);
             default:
-                return new IdentifierToken(HashedString(s), start, s.length());
+                return new IdentifierToken(HashedString(new u16string(s)), start, s.length());
         }
     }