Implement a least breaking approach to slash commands (#39)

* Most slash command support completed, needs some debugging (and reindent)

* Implement a ctx.send helper for slash commands

* Add group command support

* Add Option converter, fix default optional, fix help command

* Add client.setup and move readying commands to that

* Implement _FakeSlashMessage.from_interaction

* Rename normmal_command to message_command

* Add docs for added params

* Add slash_command_guilds to bot and decos

* Fix merge conflict

* Remove name from commands.Option, wasn't used

* Move slash command processing to BotBase.process_slash_commands

* Create slash_only.py

Basic example for slash commands

* Create slash_and_message.py

Basic example for mixed commands

* Fix slash_command and normal_command bools

* Add some basic error handling for registration

* Fixed converter upload errors

* Fix some logic and make an actual example

* Thanks Safety Jim

* docstrings, *args, and error changes

* Add proper literal support

* Add basic documentation on slash commands

* Fix non-slash command interactions

* Fix ctx.reply in slash command context

* Fix typing on Context.reply

* Fix multiple optional argument sorting

* Update ctx.message docs to mention error instead of warning

* Move slash command creation to BotBase

* Fix code style issues with Black

* Rearrange some stuff and add flag support

* Change some errors and fix interaction.channel fixing

* Fix slash command quoting for *args

Co-authored-by: iDutchy <42503862+iDutchy@users.noreply.github.com>
Co-authored-by: Lint Action <lint-action@samuelmeuli.com>

discord/client.py

@@ -624,7 +624,7 @@ class Client:
     async def start(self, token: str, *, reconnect: bool = True) -> None:
         """|coro|
 
-        A shorthand coroutine for :meth:`login` + :meth:`connect`.
+        A shorthand coroutine for :meth:`login` + :meth:`setup` + :meth:`connect`.
 
         Raises
         -------
@@ -632,8 +632,21 @@ class Client:
             An unexpected keyword argument was received.
         """
         await self.login(token)
+        await self.setup()
         await self.connect(reconnect=reconnect)
 
+    async def setup(self) -> Any:
+        """|coro|
+
+        A coroutine to be called to setup the bot, by default this is blank.
+
+        To perform asynchronous setup after the bot is logged in but before
+        it has connected to the Websocket, overwrite this coroutine.
+
+        .. versionadded:: 2.0
+        """
+        pass
+
     def run(self, *args: Any, **kwargs: Any) -> None:
         """A blocking call that abstracts away the event loop
         initialisation from you.
@@ -722,7 +735,7 @@ class Client:
         """:class:`.Status`:
         The status being used upon logging on to Discord.
 
-        .. versionadded: 2.0
+        .. versionadded:: 2.0
         """
         if self._connection._status in set(state.value for state in Status):
             return Status(self._connection._status)