[#397] Kickstart colors for Smartdocs

[zakiya]

• Creates apigee_kickstart/smartdocs library attached to field_apidoc_spec.
• apigee_kickstart/smartdocs contains a CC file that uses ak- variables to override colors.

[arlina-espinoza]

LGTM! Thanks @zakiya

[arlina-espinoza]

@zakiya Does this seem accurate to add to the docs?

OpenAPI specs are rendered by default using Apigee's SmartDocs custom field formatter. It is possible to override the styles to match your custom theme by doing the following steps:

1. In your theme's directory, create a CSS stylesheet that replaces the SmartDocs theming. You can use Apigee Kickstart's styles as a guide. Let's assume the new file is: css/my-smartdocs-styles.css
2. In your theme's info file, overwrite the stylesheet for the SmartDocs widget with your own styles. Example themename.info.yml:

libraries-override:
  apigee_kickstart/smartdocs:
    css:
      theme:
        assets/css/apigee-kickstart.smartdocs.css: css/my-smartdocs-styles.css