docs(readme): fix example code to use useQuery hook and TypeScript types

[mackenziemcclaskey]

Summary

• Adds useQuery to the import list and shows a realistic data-fetching component in the example
• Adds proper TypeScript types (ReactNode) to AppProvider so the snippet compiles without errors
• Replaces the placeholder EventListPage import (which no longer exists in the scaffold) with a self-contained ComponentWithData example

Test plan

• Read through the updated example in README and verify it makes sense end-to-end
• Confirm the snippet would compile with the correct imports from @workday/everywhere

🤖 Generated with Claude Code

[mpfilbin]

This tripped me up today. Thanks for updating the docs!