Better Codegen: Pagination Support

**Is your feature request related to a problem? Please describe.**
Is there any chance codegen can be enhanced to allow for pagination out of the box? It'd be great to not have to write my own queries.ts with this ability.

**Describe the solution you'd like**
Take a model like this:
```
type User @model {
id: ID!
todos: [Todo] @connection(fields:["id"])
}

type Todo @model {
id: ID!
userID: ID!
user: User @connection(fields:["userID"]
}
```

As codegen operates currently, a queries file will be generated that looks something lik:

```
export const getUser =
GetUser($id: ID!) {
getUser($id: ID!) {
id
todos {
items {
id
}
}
}
}
```

To my understanding, pagination can only be achieved by then implementing a custom query like so:

```
export const getUser =
GetUser($id: ID!, $limit: Int, $nextToken: String) {
getUser($id: ID!, $limit: Int, $nextToken: String) {
id
todos(limit: $limit, nextToken: $nextToken) {
items {
id
}
}
}
}
```

I think this is a fairly easy opportunity to automate this process with codegen.

**Describe alternatives you've considered**
I use string interpolation to implement this functionality but it's really annoying when the schema changes to have to re-update the query.