[V3] Custom context class (#988)

* Create custom context class

* Documentation

* Remove old help method, replace with new

* Update from rebase

redbot/core/context.py

@@ -0,0 +1,42 @@
+"""The purpose of this module is to allow for Red to
+further customise the command invocation context provided
+by discord.py.
+"""
+
+import discord
+from discord.ext import commands
+
+__all__ = ["RedContext"]
+
+TICK = "\N{WHITE HEAVY CHECK MARK}"
+
+
+class RedContext(commands.Context):
+    """
+    Command invocation context for Red.
+
+    All context passed into commands will be of this type.
+
+    This class inherits from
+    :py:class:`commands.Context <discord.ext.commands.Context>`.
+    """
+
+    async def send_help(self):
+        """Send the command help message."""
+        command = self.invoked_subcommand or self.command
+        pages = await self.bot.formatter.format_help_for(self, command)
+        for page in pages:
+            await self.send(page)
+
+    async def tick(self):
+        """Add a tick reaction to the command message.
+
+        :return: ``True`` if adding the reaction succeeded.
+        :rtype: bool
+        """
+        try:
+            await self.message.add_reaction(TICK)
+        except discord.HTTPException:
+            return False
+        else:
+            return True