feat: split app from framework

[brent-hoover]

Major restructure that breaks out the an example app from the core framework. Lots of moving stuff around and breaking out the actual loading of plugin files between example app and core. Still some issues:

• Auth plugin is still sort of split between core and plugin. Where should it live? Don't really want to have people copy the auth plugin in, but also would like to make it optional if they want to roll their own auth.
• Still have to drop actual files into a plugins directory. Is that a bad thing? Should we have the option to use files OR import from a package. Especially since Typescript seems to make it really easy to have virtual packages. 🤷 One big advantage of being able to import directly from an npm package would be where there are community packages available that people want to use and not just copy the files in.

As of this PR being opened the app doesn't fully load when the cart and discount plugins are installed as I get a graphql error. Still working on that which is why it's still a draft but that's a small implementation detail