Add FAQ entry on ca.crt

[SgtCoDFish]

We regularly see people using ca.crt or requesting it be changed. This FAQ entry is intended to be something we can link to in those situations to try and clarify why it can be dangerous!

[netlify[bot]]

✅ Deploy Preview for cert-manager-website ready!

Name	Link
🔨 Latest commit	f6725cce93f1a92d774c465e788c91dd58cd3d09
🔍 Latest deploy log	https://app.netlify.com/sites/cert-manager-website/deploys/65a131d384816200080efa07
😎 Deploy Preview	https://deploy-preview-1386--cert-manager-website.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.

[jetstack-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: jakexks

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files: - ~~[OWNERS](https://github.com/cert-manager/website/blob/master/OWNERS)~~ [jakexks] Approvers can indicate their approval by writing `/approve` in a comment Approvers can cancel approval by writing `/approve cancel` in a comment

[jakexks]

/lgtm

[SgtCoDFish]

Thanks very much @jakexks - happy new year!