Relay client-side fetch requests to the server using the Storybook channel API

[ghengeveld]

Fixes #312

This adds a ChannelFetch utility and useChannelFetch hook. ChannelFetch listens for messages on the serverChannel, performs fetch requests, and sends back a message with the response. The goal is relay client-side requests to the server, in order to avoid polluting the network request log in DevTools.

A useChannelFetch hook is included, which returns a fetch compatible function. This fetch replacement is passed to the URQL Client so all GraphQL requests will happen over the channel. Requests time out after 30 seconds (if they haven't already). The signal property is supported by means of a dedicated abort message.

📦 Published PR as canary version: 1.9.0--canary.331.67b13f2.0

✨ Test out this PR locally via:

npm install @chromatic-com/[email protected]
# or 
yarn add @chromatic-com/[email protected]

[ndelangen]

I did not test it, but the code look great to me!