propTypes bindings

Make it possible to use React propTypes to generate props for your component.

```ts
import { fromPropTypes } from 'kitimat-prop-types';
jest.mock('prop-types', () => require('kitimat-prop-types/mock'));

import { App } from './app';

const propsGen = fromPropTypes(App);

// ...
```

Already squating on `kitimat-prop-types` in packages.

The issue names the intended fromPropTypes(App) API and the kitimat-prop-types/mock module, but no source files or tests. Start by locating the existing prop-generation entry points and package setup, then verify the React propTypes example works with Jest. Done means React propTypes can generate component props through the shown API.

Written by the indexing model from the issue text.