chore: add Node.js Agent v12.8.0 Release Notes

[newrelic-node-agent-team]

This is an automated PR generated when the Node.js agent is released. Please merge as soon as possible.

[github-actions[bot]]

Hi @newrelic-node-agent-team 👋

Thanks for your pull request! Your PR is in a queue, and a writer will take a look soon. We generally publish small edits within one business day, and larger edits within three days.

We will automatically generate a preview of your request, and will comment with a link when the preview is ready (usually 10 to 20 minutes).

[netlify[bot]]

✅ Deploy Preview for docs-website-netlify ready!

Name	Link
🔨 Latest commit	5e317b23c0197264947571065fc2b1c1997e680b
🔍 Latest deploy log	https://app.netlify.com/sites/docs-website-netlify/deploys/673f25ac1ca5490008b8d616
😎 Deploy Preview	https://deploy-preview-19332--docs-website-netlify.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]]

[!NOTE]

Our Vale automated writing feedback tool has suggestions for this PR. You can view these suggestions in the Files changed tab. If you're not a New Relic docs writer, we'll review any comments and you don't need to take any action (though feel free to make edits if you like!).

[github-actions[bot]]

[!NOTE]

Our Vale automated writing feedback tool has suggestions for this PR. You can view these suggestions in the Files changed tab. If you're not a New Relic docs writer, we'll review any comments and you don't need to take any action (though feel free to make edits if you like!).

[github-actions[bot]]

[!NOTE]

Our Vale automated writing feedback tool has suggestions for this PR. You can view these suggestions in the Files changed tab. If you're not a New Relic docs writer, we'll review any comments and you don't need to take any action (though feel free to make edits if you like!).