Update README.md testing instructions

[frankfaustino]

JavaScript code in this repo uses the Jest framework for testing. The tests are contained in either a __tests__, __test__ or tests directory (I know... consistency isn't my strong suit). To run them, use the following command(s):

# replace this placeholder with explanations
npm test -- --testPathPattern="$(basename "$PWD")"
# qwerty
npm test -- --testPathPattern="$(basename "$PWD")" --watch
# qwerty
npm test <directory_name>

---

Rust code in this repo uses the testing framework included in the Rust standard library. The unit tests are contained in the same file (i.e., main.rs) as the code being tested, using a conditional compilation module named tests that is only compiled when running tests. To run them, use the following command(s):

# asdfas
cargo test
# asdfas
cargo run

---

Python code uses the unittest testing framework included in the Python standard library. The tests are contained in a tests directory. Some of the tests are just print statements in the same file as the code being tested. To run them, use the following command:

# qwrasfgsa
python3 tests/<filename>
# qwrasfgsa
python3 main.py