Provide technical documentation as docblock comments on types

This way our editors LSP will be able to help us read your documentation without leaving our editor.

Since it's all typescript, i'm only asking for narrative documentation to help explain why someone would want to use particular types.

This might also be an opportunity to create a parser for keystatic that can take in a glob of typescript files and produce content nodes, resulting in the ability to produce technical documentation websites that can intermix natural approachable content with snippets from the parsed code comments.

It's also a chance to start introducing some accountability in the architecture decisions so that team work can scale async, if it was explained in comments what the usecase and purpose of CollectionEntry vs Entry was, then refactorings/additions would be less tedious and shocking in the long run.

The issue names no files, so first locate the TypeScript definitions for CollectionEntry and Entry and read their surrounding usage. Clarify whether the goal is narrative docblock comments on the types only or also the proposed parser and documentation-site workflow. Done should mean the agreed types explain their purpose and use cases in editor-visible comments.