Adding custom blocks to Navigation menus

[paaljoachim]

Hey

I posted in the Make WordPress Slack channel for feature website navigation:
https://app.slack.com/client/T024MFP4J/C01KDAZJMQ9

It would be great to have a code snippet to where one can add additional blocks to the Navigation menus.
@ndiego

Thanks.

[ndiego]

Closing in favor of #355