Add cert-manager graduation self-assessment

[SgtCoDFish]

This PR adds the self assessment for cert-manager, which was reviewed in this Google doc.

This is also the final part of the presentation issue ( #1254 ). cert-manager was presented to tag-security in the EMEA meeting on 2024-05-22.

This is part of cert-manager's graduation issue, which is cncf/toc#1306

[netlify]

✅ Deploy Preview for tag-security ready!

Name	Link
🔨 Latest commit	d154059
🔍 Latest deploy log	https://app.netlify.com/sites/tag-security/deploys/666925a7c0e19600083c36ae
😎 Deploy Preview	https://deploy-preview-1269--tag-security.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[SgtCoDFish]

NB: I'm on holiday from 2024-06-13 and won't be reachable. If this is reviewed while I'm away I'll try to get back to this around 2024-06-24!

[anvega]

Enjoy your holiday, @SgtCoDFish! Thanks for all the hard work on this and everything you do – it really shows!

[SgtCoDFish]

Thanks very much 😁