New task provider: Check unpublished (draft/pending) content

[aristath]

Context

Sometimes people start writing a post but never finish it.
This task-provider checks for any draft/pending posts that were created more than a week ago, and then adds a new task to remind users they should review that post and maybe publish it.

Task Title

Task title: Publish {POST_TYPE} "{POST_NAME}"
Example: `Publish post "Sample Post"

In case the draft post doesn't have a title yet, the message will be Add a title to {POST_TYPE} {POST_ID} and publish it.
Example: Add a title to post 35 and publish it

Task Description

You started writing %1$s, but never finished it. Perhaps it's time to publish it?
Examples:

• You started writing "Sample Post", but never finished it. Perhaps it's time to publish it?
• You started writing post 35, but never finished it. Perhaps it's time to publish it? (in case the post doesn't have a post-title yet

[github-actions]

Test on Playground
Test this pull request on the Playground or download the zip.

[tacoverdo]

@aristath Does it only do this for the post types marked as 'valuable content'?

[ilicfilip]

@tacoverdo , yes