Add plugin system

[KyleJune]

Currently it's possible to add tools like react query and twind but requires users create there app and server using the custom providers or renderToReadableStream functions to add the additional behavior.

It would be nice to have plugins that can define custom providers and renderToReadableStream functions so that all you have to do is add the plugin to your settings instead of having to figure out how to create the providers or renderToReadableStream functions yourself.

This would make adoption easier and might lead to others making their own plugins to share with others.

Plugins would have a server and app version. They would need to be composible so that if you provide a list of plugins, it will combine them without conflicts.

After creating the plugins interface, implement twind and react-query plugins and update the examples to use them.