New Stuff
* Support new API "resolved" object
* `USER`, `CHANNEL`, and `ROLE` options are now passed as types `Union[discord.<type>, discord.ext.slash.Partial<type>, discord.Object]` (exception: `USER` arguments can also be of type `discord.User`)
* `Context.author` is now `Union[discord.Member, discord.ext.slash.PartialMember, None]` - second thanks to new changes, third because slash commands can be run in DMs with no member context
* If `SlashBot` kwarg `resolve_not_fetch=True` (the default), no fetching or getting is attempted if the object can be resolved
* If `SlashBot` kwarg `fetch_if_not_get=True` (default `False`), no API fetching is attempted if getting from bot cache fails
* `Command.created_at` is now available
Changes
* `Context.author` is now no longer guaranteed to be a `discord.Member` (it is now `Optional[discord.Member]`) because slash commands can be run in DMs now which have no member context
* `Context.guild` is now `Union[discord.Guild, discord.Object, None]` instead of a guaranteed Object for the same reason
* `Context.me` is now `Union[discord.Member, discord.Object]` instead of `Optional[discord.Member]` to be consistent
* Parameters to command coroutines that are required by the coro now automatically have their `Option.required` set to `True` regardless of the previous value
* Parameters to command coros that are required by the coro but cannot have values passed to them by the library/API (i.e. not annotated with a `Context` subclass or `Option` instance) now cause a `TypeError` on declaration of the command