added copilot instructions

[erikpanzer]

This pull request adds comprehensive developer documentation for the Smart Village App, focusing on architecture, workflows, and best practices. The new .github/copilot-instructions.md file serves as a central resource for onboarding and ongoing development, outlining the provider hierarchy, setup steps, build commands, code organization, testing strategies, and integration points.

Documentation improvements:

• Added .github/copilot-instructions.md with an overview of the app's provider-based architecture, including a detailed hierarchy of React Context Providers as implemented in src/index.js.
• Documented developer setup workflows, including handling of secrets, build and run commands, and testing procedures.
• Provided guidelines on modular screen and component organization, configuration management, and consistent UI design through the app design system.
• Explained GraphQL/Apollo integration details, including caching, authentication context, and query organization.
• Outlined cross-platform specifics, patch management, integration with external services, and the application's data flow pattern.