Create 0008-backstage.md

[dwelsch-esi]

Added Backstage doc assessment.

resolves: https://github.com/cncf/techdocs/issues/182

[nate-double-u]

@thisisobate, could you help @dwelsch-esi with the website/technology part of this assessment?

Edit, the Website section I mean:

• SEO, Analytics, and site-local search
• HTTPS access & HTTP redirect
• Google Analytics 4 for production only
• Indexing allowed for production server only
• Intra-site / local search

[thisisobate]

Sure @nate-double-u I'm happy to help

[nate-double-u]

The DCO check is failing, but I don't think that's a problem. We'll squash this PR when we merge it and can sign that commit.