feat(fetch-router): add alias functions for standard HTTP verb paths

[aaronjordan]

Drafted an idea I had watching the reveal livestream. This PR adds functional aliases for simple HTTP routes.

The route objects returned are super simple here, but providing them as functions to call would make the framework appear more consistent when defining a route using helpers. For instance, this would be an existing way to express some routes:

let routes = createRoutes({
  home:  { method: 'GET', pattern: '/' },
  books: resources('books'),
  profile: resource('profile'),
})

After this change, we would be able to use a consistent syntax for resources, formActions, and single-method routes.

let routes = createRoutes({
  home: get('/'),
  books: resources('books'),
  profile: resource('profile'),
})

I followed the resource.ts file to try to get the style right, please do advise on anything I could update!

[aaronjordan]

Would this actually go under a new 0.7.0 heading?

[sergiodxa]

The CHANGELOG is updated when a release is created, this if merged would not be part of an already released version

[mjackson]

Thanks for the PR, @aaronjordan. I had the same thought. Could you please also add helpers for head, patch, and options? That would complete the set of supported request methods.

Also, I'd like to see a test along with this work that asserts the types are still what we expect them to be when these helpers are used in a larger route config.

As for the CHANGELOG, we include new changes under a ## Unreleased heading at the top of the CHANGELOG that gets swapped out with the release version when we cut a new release.