idea for labels for lesson status

[tracykteal]

One thing we've talked about is have a lesson status, so we can know when lessons are being actively taught or retired, or in development.

A similar idea came up on r-lib about the lifecycle of an R package. This might also be a useful framework for lesson status.

https://github.com/r-lib/usethis/issues/48#issuecomment-340772064

They could have similar badges associated with them too.