Use structure to extract operation name from Cell's QUERY

[peterp]

We want to make mocking data in Storybook and Jest super simple. In order to achieve that we need to be able to get the operation name from a QUERY export in a Cell:

export const QUERY = gql`query <i.want.this.operation.value> { invoices { id } }`

• Add a way to get the operation name of the QUERY export in a Cell.
• Add diagnostic to recommend that a user should name their QUERY operation in a Cell.
• Throw an diagnostic if the template literal cannot be parser.

/cc @aldonline