Ability to upload and update add-ons

[Tosox]

I started working on these features a long whole ago, since I wanted to create a GitHub workflow which allows to update add-ons on ModDB automatically. I wondered what your opinion about these enhancements would be.

https://github.com/ClementJ18/moddb/compare/develop...Tosox:moddb:develop?expand=1

[ClementJ18]

My main concern with this library is to try and avoid implementing anything that's abusive of the website but this seems fine. The library side validation is a good idea.

As for the specific implementation, I don't have any huge issues with the individual function but I think this should be extracted into its own object. I was thinking something like MutableAddon or MutableFile (are there any differences between a file and addon?), this would allow us to move the validation logic away from the Client class since other uploadable entities may have different requirements for the same fields.

[Tosox]

Yeah, I am not happy with the code yet, I just wanted to make it functional. Also, I am not even sure how to make the code clean.