Return type of Cmfcmf\OpenWeatherMap\Util\Unit::jsonSerialize() should either be compatible with JsonSerializable::jsonSerialize(): mixed, or the #[\ReturnTypeWillChange] attribute should be used

[jamieburchell]

Version: v3.3.1
PHP: 8.1
Error:

A PHP Error was encountered
Severity: 8192

Message: Return type of Cmfcmf\OpenWeatherMap\Util\Unit::jsonSerialize() should either be compatible with JsonSerializable::jsonSerialize(): mixed, or the #[\ReturnTypeWillChange] attribute should be used to temporarily suppress the notice

Filename: Util/Unit.php

Line Number: 155

[jamieburchell]

Looks like this would fix it