Option for a more express-like routing API

[danvk]

Normally with Express, the router API looks like this:

router.post('/path/:param', (request, response) => {
  const {params, body} = request;
  // ...
});

The crosswalk equivalent looks like:

typedRouter.post('/path/:param', (params, body, request, response) => {
  // ...
});

There's no reason crosswalk couldn't provide an equivalent of the express post that just takes request and response params but types their body & params properties. This might make migration simpler and would remove some awkwardness when you want the request param but don't have path params or a body.