Feature: keystaticToAstroCollections

As mentioned in https://youtu.be/6l2YWCyPsWk, it would be great to have a keystaticToAstroCollection utility exported by @keystatic/astro to translate the Keystatic config to the Astro collections config.

Example usage:

// src/content/config.ts
import keystaticConfig from "../../keystatic.config"
import { keystaticToAstroCollection } from "@keystatic/astro"

const keystaticCollections = keystaticToAstroCollection(keystaticConfig)

export const collections = {
	...keystaticCollections
}

I made some experiments at the type level but collections and singletons specific types are lost once past to the config

Start with the src/content/config.ts example, the imported keystatic.config, and the @keystatic/astro package entry point. Trace how collection and singleton types are represented and where they are lost in the configuration flow. Done means the package exports keystaticToAstroCollection and the example produces an Astro collections configuration with those specific types preserved.