Add best practices document about Hub manifests

[mszostok]

Description

Add document about best practices for storing and creating Hub manifests.

Describe:

• Hierarchy, e.g. prefer cap.interface.database.postgresql instead of cap.interface.postgres
• How populator stores data e.g. generated path. Currently, they are calculated from dir structure (hierarchy).
• How to deal with multiple revisions for the same Action. Currently, we use file names, e.g. install-0.0.1, install-0.2.1

Reason

"Consistent code is easier to maintain, is easier to rationalize, requires less cognitive overhead, and is easier to migrate or update as new conventions emerge or classes of bugs are fixed."

• It's easier for us to review community PRs.
• External contributors don't need to figure out the correct approach each time they create manifests.

Use cases

• Content Developer - knows how to create quality, good content.

[mszostok]

Description moved to: #8