feat: added a guide for the passkey integrations

[jhickmanit]

Related Issue or Design Document

Checklist

• I have read the contributing guidelines and signed the CLA.
• I have referenced an issue containing the design document if my change introduces a new feature.
• I have read the security policy.
• I confirm that this pull request does not address a security vulnerability.
  If this pull request addresses a security vulnerability,
  I confirm that I got approval (please contact security@ory.com) from the maintainers to push the changes.
• I have added tests that prove my fix is effective or that my feature works.
• I have added the necessary documentation within the code base (if appropriate).

Further comments

[vinckr]

overall lgtm,
a few style issues and sidebar is missing.
let me know if I can help with sidebar, im quite familiar with it.

only nit is that I would prefer the troubleshooting part to be a separate doc under https://www.ory.com/docs/category/troubleshooting and that the doc is maybe a bit overly verbose, but that is more a personal preference ;)

[jhickmanit]

If you could help with the sidebar and feel free to split the troubleshooting to a different document for sure!

[vinckr]

needs a redirect bc 06_code.mdx has been renamed to 07_code.mdx

actually doesn't need redirect