[meta] Docs templates for Drupal 8

Problem/Motivation

With much of the current Drupal 8 documentation, after finding an article, it can be hard to find the important information in the article. This is an old issue, but as Drupal 8 is still highly un-documented compared to earlier versioned documentation pages, it could be especially impactful to recommend new, easy to use templates that will increase accessibility, navigability, and ease of use for all audiences.

Proposed resolution

Make templates to guide docs creation in a more structured, consistent way. Possibly all we would need are the 3 "modular structure" topic types from Documentation writers guide: Concept, Task, and Reference.

Rather than lengthy articles that try to cover a number of concepts and tasks, information should be broken down into the smallest units that can stand alone. In other words, a single node should only address a single topic (task, concept or reference item). Do not mix tasks with conceptual information.

^^^------- THIS!

This meta issue is to be the parent for subsequent issues to track each individual template.