Add more GraphQL Schema Design Guidlines

We have a page for Schema Design https://graphql.org/learn/schema-design/

I think we should add lots more entries to this page!

There's lots of well-established principles and conventions already, see https://github.com/magicmark/awesome-graphql-schema-design

Not everything is universally applicable. We should seek to only upstream things that make sense to 99% of users, or add clarification statements for things that are less universally true but still largely true.

For any non-trivial additions, I would propose we review PRs either in the main wg or golden path wg (cc @benjie) meetings?

Let's create sub-issues for each topic.

_(This ticket is being made as an action item from Golden Path WG Mar 12th 2026)_