Injecting MAC address into MQTT device topics

[latonita]

Description:

mac address injection into mqtt topics + <topic_prefix> placeholder

Related issue (if applicable): fixes https://github.com/esphome/feature-requests/issues/2504

Pull request in esphome with YAML changes (if applicable): esphome/esphome#6273

Checklist:

• [X] I am merging into next because this is new documentation that has a matching pull-request in esphome as linked above.
  or

• [ ] I am merging into current because this is a fix, change and/or adjustment in the current documentation and is not for a new component or feature.

• [ ] Link added in /index.rst when creating new documents for new components or cookbook.

[netlify[bot]]

✅ Deploy Preview for esphome ready!

Name	Link
🔨 Latest commit	c13c48276ba5b06f779d99d47c05ea55fdb5365a
🔍 Latest deploy log	https://app.netlify.com/sites/esphome/deploys/65da5004664c630008aa2700
😎 Deploy Preview	https://deploy-preview-3634--esphome.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.

[github-actions[bot]]

There hasn't been any activity on this pull request recently. This pull request has been automatically marked as stale because of that and will be closed if no further activity occurs within 7 days. Thank you for your contributions.