Added more descriptive wording for Slack channel config.

[jonathancadepowers]

Users sometimes fail to add a # character before the channel's name, which breaks the configuration. I added wording to make this clear.

[JacobNinja]

This still doesn't solve the problem of the user not providing # as a predicate to the channel name.

I think we should detect the presence of # and add it if not present. I'm happy to walk through and discuss the process of writing this code with you.

[noahd1]

Agree with @JacobNinja and think someone should write the code instead of changing the wording. After that, the wording should specify that it's optional (otherwise people will wonder)

[brynary]

This seems to have gone stale. Closing.

@jonathancadepowers feel free to re-surface as desired.