Host use case guides on about platform

Created by: elzannewentzel

Stakeholders:Fabiana What: Host our guides on the about platform and provide links. Why: Marketing can include it in collateral or share it.

Use our default Sourcegraph image for all these pieces: Dev onboarding one-pager → meta Code security one-pagers → meta Incidents response one-pager → meta Code health one-pager → meta Code reuse one-pager → meta