Change return type of `JsonValue.of` to `JsonNumber` for number arguments

[jufickel-b]

Currently all variants of JsonValue.of return a JsonValue. For number arguments, however, it is desirable to obtain a JsonNumber without being forced to manually cast. As JsonNumber extends JsonValue, changing the method signatures would be a low hanging fruit that improves ditto-json API a bit.

[jufickel-b]

Additionally it is worth to think about introducing a JsonFieldDefinition for JsonNumber.

[theexplorist]

@jufickel-b Hi I am an open source enthusiast who contributes to java projects and previous google summer of code student developer, I am looking for new challenge so can you please tell me if I can contribute here?

[jufickel-b]

Hi @theexplorist, thanks for reaching out to us. Of course you can contribute here. Before doing so, it is crucial that you have a look at CONTRIBUTING.md – especially the legal requirements.