Add more explanation of what this app is for

[david-mears-2]

As a newcomer to VIMC I'm not sure if there is a more in-depth explanation of what packit is somewhere online, besides the one sentence "Web app for serving outpack and/or orderly2 metadata" at the top of this repo's README. If there's more explanation somewhere else then we could link to it from this README.

Perhaps a screenshot of the app in action would help to convey what kind of metadata you are talking about? (Or does the app even have a front end or is it just a pure server?)