fix: clean up enum handling

[julrich]

Right now we're jumping through some hoops to get GraphQL- / TypeScript-safe enum values. Those are not safe by default, as used in our JSON schema (e.g. 16:9, or just simply 1).

We use the following code to make them safe, but it's destructive in nature:
https://github.com/kickstartDS/kickstartDS-schema-toolkit/blob/master/jsonschema2graphql/src/graphqlSafeEnumKey.ts
https://github.com/kickstartDS/kickstartDS-schema-toolkit/blob/master/jsonschema2netlifycms/src/safeEnumKey.ts

As in: you can't deterministically convert values back to their original form, once they are made safe. This is why different properties (like ratio or pattern) need to be handled explicitly here, to reconstruct the needed format. As properties can be customized from a project-level (e.g. pattern already is an individualization for kickstartDS/design-system) we can't have custom handling per property here. At least in the long run!

Another difference is the handling of - vs _. Should be consistent, and need no extra handling while converting.

Also see the TODOs here: https://github.com/kickstartDS/gatsby-theme-kickstartDS/blob/master/gatsby-theme-kickstartds/src/components/KickstartDSPageComponent.tsx#L47-L52