* added UserDefaultAvatar to IUser

* pass ushort as discriminator

* removed unneeded ushort.parse

- Add a helper under CDN for cover art URLs
It would be bad practice of us to leave CDN urls hardcoded in the
deserializer, would be harder to change down the line should Spotify
ever change their CDN.

I'm not entirely supportive of leaving Spotify's CDN hardcoded in our lib
either, but there's no better alternative.

- Change SpotifyGame#Artists to an IEnumerable<string>
Seems pretty common to prefer IEnumerables in place of Arrays.

* Added support for animated emoji

This was such a useful feature Discord, I'm glad you added this instead
of fixing bugs.

* Fix bugs in emote parser

* Added unit tests for emotes

* Add API-level support for Rich Presences

* Add library-level support for Game presences

* Add model conversions for outgoing+incoming rich presences

* Refactored Game into Activities

* Integrated Activities with user entities

rebase hell from 5f3cb947a9

* Fix JSON converters for Activities

* Finish rebase, activity should be set on BaseSocketClient

* Use ApplicationId to define a rich presence

* Added SetActivityAsync to Base and Sharded Socket clients

* Remove public parameterless Game constructor

* Remove GameAssets, refactored to GameAsset

* Hide constructors for types that should be read-only

* Revert changes to Discord.Net.sln

got damned visual studio caching

* Refactor GameParty to use dedicated current/capacity values

Per feedback from @khionu

This is to support the new user image endpoint, which provides a parameter for image resizing.