add custom command checks tag

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diff --git a/bot/resources/tags/customchecks.md b/bot/resources/tags/customchecks.md
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+**Custom Command Checks in discord.py**
+
+You may find yourself in need of a decorator to do something that doesn't exist in discord.py by default, but fear not, you can make your own! Using discord.py you can use `discord.ext.commands.check` to create you own decorators like this:
+```py
+from discord.ext.commands import check, Context
+
+def in_channel(*channels):
+  async def predicate(ctx: Context):
+    return ctx.channel.id in channels
+  return check(predicate)
+```
+There's a fair bit to break down here, so let's start with what we're trying to achieve with this decorator. As you can probably guess from the name it's locking a command to a list of channels. The inner function named `predicate` is used to perform the actual check on the command context. Here you can do anything that requires a `Context` object. This inner function should return `True` if the check is **successful** or `False` if the check **fails**.
+
+Here's how we might use our new decorator:
+```py
[email protected](name="ping")
+@in_channel(728343273562701984)
+async def ping(ctx: Context):
+  ...
+```
+This would lock the `ping` command to only be used in the channel `728343273562701984`.