Adds support for the "other" category In sprites

[Deleca7755]

Sorry If It succ I never make significant pull requests or... program at all often ( only recently started a meaningful project which I'm using your library for ), but It worked for me

[beastmatser]

First of all thank you for contributing, I just have a few remarks about the code you wrote. I would like to keep the original structure of the data that is collected, meaning that the additions you made should be accesed by pokemon.sprites.other.dream_world for example. So, Other should get its own class and that is where the three attributes should be put. Also notice that the class DreamWorld and OfficialArtwork are identical, therefore I believe it would be best to make a parent class and then define both classes by just inheriting from this newly made class. Lastly, you correctly check if the other attribute could be None by using an if-structure. Instead, you could use a one-liner for this, this is a purely asthetic chance made for consistency. Thank you!

Code was already adequate