Images in app descriptions overflow on hover

[Bubballoo3]

From discourse https://discourse.openondemand.org/t/hovering-issue-of-manifest/4679.

Images included in the description of an app's manifest.yml are rendered in the popup but overflow and fill the screen.

All we need to fix this is to add the following html rule

.popover-body img {
   max-width: 100%
 }