Support a QR Code

Let's help people who put "We're hiring!" at the end of their presentations, it'd be nice to have the project logo, QR code, etc. in one widget that's condusive to this.

Additionally make a top level one for gitjobs.dev so that we can put it in the CNCF templates. Then the projects can just slice and dice however they want to present the data. 😄

The issue names no files, tests, or entry points. Start by locating the existing presentation widgets and template integration, then clarify the expected QR-code content, widget API, and CNCF template requirements. Done should include an agreed design and working project-level and gitjobs.dev presentation components.

Written by the indexing model from the issue text.