Introduce createServer

[dfreeman]

@samselikoff we had a conversation about this a little over a month ago, and I went and implemented it but then never actually committed the files and opened a pull request 🤦

This PR introduces a createServer function as an alternative to writing new Server. While it doesn't add any new functionality, it does have a couple of advantages:

• It avoids having consumers of the library call a side-effecty constructor (whether that's a code smell or not is a matter of personal opinion, but it's certainly been the topic of lots of angsty blog posts)
• It allows for type-safe interactions with the server in the context of your config, which was the last lingering topic of discussion in Using mirage of versions above 0.1.35 fails to build and run #396.
  In other words, if I write schema.all('foo') in a route handler, TypeScript can tell based on the foo model/factory I provide what type the result will have. Or, if I haven't provided a foo model, it can correctly flag schema.all('foo') as an error.

/cc @zoltan-nz @chriskrycho

[samselikoff]

Awesome!! Thank you so much for this, I know it will make TS users happy 🙏

@chriskrycho @zoltan-nz any chance y'all could take a quick look or give it a shot in your TS projects?

[zoltan-nz]

@samselikoff Thanks for the heads up.

@dfreeman Brilliant improvement. Love it.

I give it a try today in my project, however it looks good to me already.

[zoltan-nz]

@samselikoff I played with it and works like a charm. Thanks. :)

[jamescdavis]

This is great!

[chriskrycho]

👍 looks good here!

[samselikoff]

Amazing – thanks everyone!