Include MR's assigned in User callout
## Description As a MR author, I'd like to know the availability of a member before assigning to them. Maybe we could include the number of MR's authored in the user callout? It'd be *really* nice to see the number of MR's they are reviewing (which is sort of the `MR's assigned that are not authored`). ![Screen_Shot_2019-08-29_at_12.08.00_PM](/uploads/7617a31b2d20e41dd1aff1f6506a4535/Screen_Shot_2019-08-29_at_12.08.00_PM.png) /cc @jramsay @andr3
issue