Avoid waiting for message when bot will not see it

Previously, the code below the if-statement will always execute if eat
is False. In guilds where the bot only has the applications.commands scope, or guilds
with the bot scope where the bot cannot read the channel's messages, the bot will
not find SlashContext.message and will time out after 3 seconds. This unnecessary
wait slows down command execution.

With this change, the bot will only check for messages if one of the
following conditions are true:
- SlashContext.guild_id is None (i.e. command executed in a private DM)
or
- SlashContext.channel is not None (i.e. command executed in a guild with the bot scope),
and the bot has permission to view messages in the command's channel.

Author: MichaelJHarvey

discord_slash/context.py

@@ -91,7 +91,7 @@ async def respond(self, eat: bool = False):
         base = {"type": 2 if eat else 5}
         _task = self.bot.loop.create_task(self._http.post(base, self.interaction_id, self.__token, True))
         self.sent = True
-        if not eat:
+        if not eat and (not self.guild_id or (self.channel and self.channel.permissions_for(self.guild.me).view_channel)):
             with suppress(asyncio.TimeoutError):
                 def check(message: discord.Message):
                     user_id = self.author_id