Include config section in bundle docs for env vars

[vanstee]

Man pages generally have a config section for env vars or general configuration. Since our bundles have similar needs, let's include a section like that for bundles when there's a clear need.

[kevsmith]

Can we do this without requiring another bundle config version bump? If so, I'm all for it. If not, let's discuss.

[vanstee]

Yup. Since it's optional, I think we'll be ok just including it without a version bump.