Add CI for linting, type-checking, and (maybe) deployment

[karlhorky]

There are unresolved lint errors on these lines, but we don't know about them:

https://github.com/upleveled/graphql-example-spring-2023-austria-vienna/blob/1653b434dd3fdbe7130b8387404734335c960fc6/app/api/graphql/route.ts#L191-L197

We should have a CI (and maybe CD - deployment) pipeline like we do in the Next.js example:

https://github.com/upleveled/next-js-example-spring-2023-vienna-austria/blob/main/.github/workflows/test-playwright-and-deploy-to-fly-io.yml

[karlhorky]

Also added another one (which should be fairly similar) over here:

• https://github.com/upleveled/external-apis-example-spring-2023-vienna-austria/issues/1