Resolve "Add MJML installation instructions in the Ubuntu Installation tutorial."

Testing Notes

• Follow the new guide in testing/vagrant_ubuntu_install/README.md
• It should setup a working Baserow locally in a VM accessible via local dns entries. Crucially with a working MJML server.
• Trigger an operation that will send an email
• Confirm that /var/log/baserow/worker.error contains the email dump
• Confirm that you can restart nuxt now with sudo supervisorctl restart nuxt
• Confirmed that Baserow is working correctly in the vm, can export, can see hosted media files, realtime is working.

Merge Request Checklist

• changelog.md has been updated if required
• Documentation has been updated
• Quality Standards are met
• The UI/UX has been updated following UI Style Guide
• The redoc API pages have been updated for any REST API changes
• The per database user API docs page has been updated for any REST API changes made to endpoints which can be accessed via a user created token
• Has performance been considered and tested when appropriate? Ideally Baserow should be performant when working with hundreds of thousands of rows
• New/Changed Premium features are separated correctly in the premium folder
• There are tests for and it has been checked that any changed/new django ORM code is sensible, doesn't perform N queries and that table models are not generated needlessly or generated with all columns when only a few are needed.

Closes #385 (closed)