Generate settings.yaml and apply strictyaml schema validation to settings during shop build replacing .env usage

[chrisjsimpson]

Is your feature request related to a problem? Please describe.

Describe the solution you'd like
Generate settings.yaml and apply schema validation to settings during shop build replacing .env usage

Describe alternatives you've considered

Additional context
https://hitchdev.com/strictyaml/

[chrisjsimpson]

See branch/issue 91-generate-settings-yaml

#91