Documentation revamp ideas

One idea is to do something like https://github.com/buildbuddy-io/rules_xcodeproj/blob/main/docs/usage.md which links out to larger examples but attempts to be the central place for discovering all the random features these rules support

Start by reading the referenced docs/usage.md example and comparing its central feature-discovery approach with the current rules_apple documentation. Done would mean agreeing on the documentation structure and covering the supported features with links to larger examples, but this issue does not identify the repository files to change.

Written by the indexing model from the issue text.