Convert vulnerability description from HAML to Vue component on Standalone Vulns page

This is the first of two issues created in an effort to convert the Standalone Vulns page into a single Vue app. Currently it's a Vue header, static content, then a Vue footer.

The scope of this issue is limited to converting the vulnerability description, which is currently in the haml template, to a Vue component.

The second issue (#214598 (closed)) will complete this effort by:

Merge everything into one Vue app so that the header and footer are components inside the app instead of separate apps. The description component from point 1 will also be in this app.