support mutliple schemas / endpoints

[DanielEngelhardt3TS]

Is your feature request related to a problem? Please describe.
I want to create an app that exposes a public-facing schema and one that only authenticated admins can use. This would also mean that the introspection of each schema would only serve the available queries/mutations/types of the respective endpoint

Describe the solution you'd like
maybe expose the yoga graphqlEndpoint-config property?

[schettn]

Hi! You currently can set the graphqlEndpoint property (although it's not typed yet).

But this would only change the endpoint of your pylon.

Running two different schemas within the same pylon is currently not possible.

In theory you could run two different apps with shared code and wrap it with a proxy.

[schettn]

Disabling introspection is now possible with the graphiql config property.

ref: #102