feat: add a test case for the function props not recalculating

[OliverGeneser]

No description provided.

[palkerecsenyi]

I've added a fix for the bug and the tests are passing now.

This code meant that extraProps was completely overwritten if it was a function, so future changes to the props didn't cause the function to be recomputed. This PR now fixes that.

export function parametrize(Component, extraProps) {
  const ParametrizedComponent = props => {
    // handle deferred prop calculation
    if (typeof extraProps === 'function') {
      extraProps = extraProps(props);
    }