Update README.md

README.md

@@ -137,3 +137,19 @@ mol2 = read_mol2(test_file)
 atoms_df = mol2['ATOM']  # The 'ATOM' category as a DataFrame.
 bonds_df = mol2['BOND']  # The 'BOND' category as a DataFrame.
 ```
+
+## Contributing
+
+1. Fork this repository
+2. Create a branch for your fix of an issue/feature/doc (`git checkout -b my-fix`)
+3. Stage your changes, run `pre-commit`, and run `pytest` until every thing looks fine
+4. Commit your changes (`git commit -am 'Added some feature/fix/doc'`)
+5. Push to the branch (`git push origin my-fix`)
+6. Create new Pull Request
+
+For code quality control, we use `pre-commit` hooks for formatting and type hints.
+
+Try your best to add test cases for bug fixes and new features. We use `pytest` for testing.
+
+For documentation, we should try to follow the [Google Python docstrings style](https://sphinxcontrib-napoleon.readthedocs.io/en/latest/example_google.html).
+