Add official external commands to manpage.

[MikeMcQuaid]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
• Have you successfully run brew tests with your changes locally?

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These are the ones that are auto-installed without tapping and it makes sense to make them more prominent in our documentation as we've offloaded various functionality over the years to each of them.

[apjanke]

👍 These are prominent enough it makes sense to have them referenced in the main man page. Formatting looks good.