Refine new tutorial posted event

[afewell]

Currently the auto-promoting features in the merge_event workflow will post notifications for new tutorials when a change is detected in the content/english/blog/ directory, this includes both when a new blog file is added or (post-approval) modified/removed.

While this is potentially acceptable for now since post-approval modifications and deletes are rare, eventually this will lead to undesirable events like new post notifications being made for old posts when deleted or archived.

This service needs to be refined to only post notifications:

1. Only when a new tutorial is added
2. AND if the tutorial's "draft" attribute is set to "false"

This plan does not account for auto-promoting after a modification to an existing tutorial file when promotion is desirable, for example a case where someone may initially post a tutorial in draft: true status and later change the value to draft: false. While handling of this case could be automated, at this time this latter use case is very rare and it appears that the benefit-to-effort ratio of automated handling for this and similar atypical use cases is not sufficient to warrant development and should remain as manually handled exceptions unless circumstances change.