fix: re-exports graphql json types for external use (#6711)

Fixes https://github.com/payloadcms/payload/issues/6683

Exports import `GraphQLJSON` and `GraphQLJSONObject` from
`@payloadcms/graphql/types`

```ts
import { GraphQLJSON, GraphQLJSONObject } from '@payloadcms/graphql/types'
```

test/custom-graphql/config.ts

@@ -1,3 +1,4 @@
+import { GraphQLJSON } from '@payloadcms/graphql/types'
 import { fileURLToPath } from 'node:url'
 import path from 'path'
 const filename = fileURLToPath(import.meta.url)
@@ -35,6 +36,11 @@ export default buildConfigWithDefaults({
           type: GraphQL.GraphQLString,
           resolve: resolveTransactionId,
         },
+        foo: {
+          type: GraphQLJSON,
+          args: {},
+          resolve: () => 'json test',
+        },
       }
     },
     mutations: (GraphQL) => {