Create graphql helpers

[wheresrhys]

I think it may be possible to wrap MSW's graphql helpers https://mswjs.io/docs/api/graphql/, or at least take inspiration from the design

[wheresrhys]

Provisional API, based on https://the-guild.dev/graphql/tools/docs/mocking#mockserver

fetchMock.post('/graphql', fetchMock.graphQL(schemaString, mocks, preserveResolvers))

graphQL: (schemaString, mocks, preserveResolvers) {
const server = mockServer(schemaString, mocks, preserveResolvers)
 return ({options: {body: {variables, query}}}) => {
    return server.query(query, variables)
}
}