Replace all instances of tox with nox

CONTRIBUTING.md

@@ -1,38 +1,31 @@
 # Contributing
 
-Use Tox to run tests and linting, e.g.
+Use [Nox](https://nox.thea.codes/en/stable/) to run tests and linting, e.g.,
 
 ```shell
-pip install tox
+pip install nox
 ```
 
+`nox` will run all checks in an isolated virtual environment with Autograd and its dependencies, including its optional dependencies, installed.
+
 ## Run tests, linting, packaging checks
 
-```shell
-tox list                # list all Tox environments
-tox run -e ruff         # run code style checks
-tox run -e py           # run tests with your default Python
-tox run -e package      # verify packaging
-tox                     # run all Tox environments
-```
+| Command                   | Description                                                                                                                                                     |
+| ------------------------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------- |
+| `nox --list`              | Lists all available Nox sessions, including selected ones                                                                                                       |
+| `nox -s lint`             | Runs code style checks with pre-commit and pre-commit hooks as listed in `.pre-commit-config.yaml`. Accepts posargs to pass additional arguments to the linter. |
+| `nox -s tests`            | Runs tests with your default Python interpreter. Accepts posargs to pass additional arguments and configuration to `pytest`.                                    |
+| `nox -s validate-package` | Builds a source distribution and a wheel using `pypa/build` and checks the package with `twine` in strict mode.                                                 |
+| `nox`                     | Runs all selected sessions, as listed in `nox.options.sessions` in `noxfile.py`.                                                                                |
 
 Make sure all tests pass before you push your changes to GitHub.
 GH Actions will run the tests across all supported Python versions.
 
-## Using arguments (reformat, upload package, help)
+## Using positional arguments (reformat, upload package, help)
 
-You can use additional arguments for the tools called by Tox by
-separating them from the Tox arguments by a double-dash `--`, e.g.
-
-```shell
-tox run -e ruff -- autograd/core.py --show-source
-tox run -e ruff -- autograd/core.py --fix
-```
+You can use additional arguments for the tools (`pytest`, `pre-commit`, etc.) called by Nox by
+separating them from the Nox arguments by a double-hyphen `--`, e.g.,
 
-```shell
-tox run -e package -- upload
-```
-
-```shell
-tox run -e py -- --help
-```
+- `nox -s tests -- --tests/test_tuple.py` runs just the tests listed `tests/test_tuple.py`.
+- `nox -s lint -- --fix` runs the linter with the `--fix` flag.
+- and so on.