Suppress deprecated notice on PHP8.1

[pyrou]

Related Issue/Intent

Resolves #235

Changes

Fix following notice

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

Breaking changes

Code is backward compatible for all currently supported php versions (^7.3|^8.0)

[atymic]

This method never returns a string so it's going to cause type errors.

[pyrou]

This method was documented as returning a string, it is calling ˋtoArray()ˋ that in its turn is documented to return a string.

In the end, it returns $value documented to hold a mixed value. So you are right, this can lead to a type error.

I'll change return type to mixed (including all related PHPdoc)

EDIT: mixed not compatible PHP ^7.3. As suggested by @spawnia, annotation ReturnTypeWillChange is used instead.

[pyrou]

Ping @BenSampo

[eduardoturconi]

ping @BenSampo

[nitrogenium]

ping @BenSampo