fix(ImageViewer.js): enlarge heading and wrap catalog screenshots
fix(ImageViewer.js): enlarge heading and wrap catalog screenshots

On a package catalog page, enlarges the "Media" heading and adds
wrapping for catalog screenshots.

Closes DCOS-20340

dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui,dcos/dcos-ui