Setup CI workflow and apply cargo fmt to entire repository

[Abd002]

Summary

This PR adds a lightweight GitHub Actions CI workflow for the repository.

It provides:

1. Format check

   • Runs cargo fmt --all -- --check
   • Ensures all Rust code, examples, and tests follow standard Rust formatting

2. Tests

   • Runs cargo test --all -- --nocapture
   • Verifies that the library and examples compile and pass all tests

3. CUPS dependency

   • Installs libcups2-dev on Ubuntu for compilation of CUPS bindings

• Automatically checks code formatting and test correctness on push and pull requests
• Keeps contributions clean, consistent, and easier for maintainers to review

Notes

• No functional changes to the library or examples
• CI is lightweight and fast, focused on formatting and correctness