Add example crates in data/test-packages

[cdstanford]

This is an open issue that would be good for everyone involved to do at least once to start out!

To add an example crate:

• make a directory in data/test-packages and run cargo init inside it
• add whatever Rust source files you want and make sure it compiles
• check the output of cargo run --bin scan -- data/packages/<your crate>. Report anything you think is weird/should be fixed

Finally, add the crate to automatically be updated on make test so that we can track the output. To do that:

• add the crate name to data/crate-lists/test-crates.csv
• run make test to check the output on your own machine.
• push your code; the GitHub actions workflow should automatically include the results in the repo on the next run.

[cdstanford]

After completing this, check out #8 for a follow-up issue to write a policy for your example crate.