chore: add contributing doc

[skip ci]

CONTRIBUTING.md

@@ -0,0 +1,112 @@
+# Contributing
+
+Please open issues to discuss enhancements and bugs that you may encounter with
+libNeuroML. Pull requests with enhancements and bug fixes are welcome.
+
+## Virtual environments and editable installs
+
+It is best to use [virtual environments](https://docs.python.org/3/tutorial/venv.html) when developing Python packages.
+This ensures that one uses a clean environment that includes the necessary
+dependencies and does not affect the overall system installation.
+
+For quick development, consider using [editable installs](https://setuptools.pypa.io/en/latest/userguide/development_mode.html).
+The dependencies are broken down in the `setup.cfg` file. To get a complete development environment, one can run:
+
+
+    pip install -e .[dev]   # an editable install with all development dependecies installed
+
+
+## Code style
+
+1. The source code uses spaces, and each tab is equivalent to 4 spaces.
+
+2. We use the [reStructuredText (reST)
+   format](https://stackoverflow.com/a/24385103/375067) for Python docstrings.
+   Please document your code when opening pull requests.
+   All methods/functions/modules *must* include docstrings that explain the parameters.
+
+3. We use [ruff](https://pypi.org/project/ruff/) to format and lint our code. (See the section on pre-commit below.)
+
+4. Please use [type hints](https://docs.python.org/3/library/typing.html) wherever applicable.
+   You can set up type checkers such as [mypy](https://mypy.readthedocs.io/) to use type hints in your development environment/IDE.
+
+
+        pip install mypy
+
+
+### Pre-commit
+
+A number of [pre-commit](https://pre-commit.com/) hooks are used to improve code-quality.
+Please run the following code to set up the pre-commit hooks:
+
+    $ pre-commit install
+
+The hooks will be run at each `git commit`.
+Please see `.pre-commit-config.yaml` for information on what hooks we run.
+
+
+### Commit messages
+
+Writing good commit messages makes things easy to follow.
+Please see these posts:
+
+- [How to write a Git commit message](https://cbea.ms/git-commit/)
+- While not compulsory, we prefer [conventional commits](https://www.conventionalcommits.org/en/v1.0.0/)
+
+
+## Tests
+
+Bug fixes and new features should include unit tests to test for correctness.
+One can base new tests off the current ones included in the `tests/` directory.
+To see how tests are run, please see the [GitHub Actions configuration file](https://github.com/NeuralEnsemble/libNeuroML/blob/development/.github/workflows/ci.yml).
+
+We use [pytest](https://docs.pytest.org/) for unit testing.
+One can run it from the root of the repository:
+
+    pytest
+
+
+To run specific tests, one can use the `-k` flag:
+
+
+    pytest -k "..."
+
+
+## Pull Request Process
+
+1. Please contribute pull requests against the `development` branch.
+2. Please ensure that the automated build for your pull request passes.
+3. Please write good commit messages (see the section above).
+
+### Updating your pull request branch
+
+Over time, as pull requests are reviewed, the `development` branch continues to move on with other changes.
+Sometimes, it can be useful/necessary to pull in these changes to the pull request branch, using the following steps.
+
+Add the upstream libNeuroML repository as a remote:
+
+
+    git remote add upstream https://github.com/NeuralEnsemble/libNeuroML.git
+
+
+Update your local copy of the `development` branch, and the remote copy in your fork:
+
+
+    git checkout development
+    git pull upstream development
+    git push
+
+
+Pull in changes from development to your branch:
+
+
+    git checkout <feature branch being used for PR>
+    git merge development
+
+
+If there are merge conflicts, you will need to [resolve these](https://git-scm.com/book/en/v2/Git-Branching-Basic-Branching-and-Merging#_basic_merge_conflicts), since merging the feature branch in the pull request will also result in these.
+After any merge conflicts have been resolved (or if there aren't any), you can
+push your branch to your fork to update the pull request:
+
+
+    git push