New fields / new paragraphs configuration - pushing updates to existing installations

[finnlewis]

Discussing #102 with @ekes and @andybroomfield

Raises the question:

If we are adding new fields to a paragraph, do we want to push the new field addition to existing installations via an update hook?

@ekes points out that we already do this in localgov_directories. An update hook checks to see if if the field exists, if not, creates the configuration: https://github.com/localgovdrupal/localgov_directories/blob/2.x/localgov_directories.install#L151

[markconroy]

I'd like us to support this. It has a better feeling of councils actually getting updates to the platform than our present system has.