title: TypeScript type for Apollo useMutation's refetchQueries?
body: <p>I have an Apollo useMutation hook with TypeScript types:</p>
  <pre><code>const MY_MUTATION = gql`
    mutation($source: String!) {
      doSomething(source: $source) {
        result
      }
    }
  `
  
  const [myMutation] = useMutation&lt;ReturnPayloadType, MutationVariables&gt;(MY_MUTATION);
  </code></pre>
  <p>Which gives me type safety when I use it:</p>
  <pre><code>myMutation({
    variables: {
      source: 'some source',
      // foo: 'bar' This would error if uncommented. 
    }
  })
  </code></pre>
  <p>This is working but now I need to use the <code>refetchQueries</code> key. How can I add types to it?</p>
  <pre><code>myMutation({
    variables: {
      source: 'some source',
      // foo: 'bar' This would error if uncommented. 
    },
    refetchQueries: [
      {
        query: MY_OTHER_QUERY,
        variables: {
          foo: 'bar' // I want to add type safety here
        }
      }
    ]
  })
  </code></pre>