Add CONTRIBUTING.md

Signed-off-by: Thomas Lauf <thomas.lauf@tngtech.com>

Author: lauft

CONTRIBUTING.md

@@ -0,0 +1,52 @@
+# Contributing to Holidata
+
+Thank you for considering contributing to Holidata!
+This document outlines how you can help maintain and update holiday data.
+
+## Maintaining Holiday Data
+
+Help keep our holiday data accurate by:
+
+1. Monitoring official government publications and legal documents
+2. Identifying changes such as:
+   - Newly established holidays
+   - Abolished holidays
+   - Date/observance rule changes
+   - Regional observance pattern updates
+   - Name/official designation changes
+
+3. Verifying against primary sources (official government documents)
+4. Updating relevant files in `src/holidata/holidays/`
+
+## Updating Holidays
+
+For guidance on how holidays are defined in the code, refer to [docs/how-tos/define-holidays.md](docs/how-tos/define-holidays.md).
+This should help you when you want to make changes.
+
+## Adding New Countries
+
+If you want to add a new country to Holidata, please follow the detailed guide in [docs/how-tos/add-country.md](docs/how-tos/add-country.md).
+Of course, we would be very happy if you could as well help to maintain this country afterward.
+
+## Adding Languages
+
+To add additional languages for a country, see [docs/how-tos/add-locales.md](docs/how-tos/add-locales.md).
+
+## Submitting Your Contribution
+
+Before you begin, make sure you have set up your development environment by following the instructions in [docs/how-tos/getting-started.md](docs/how-tos/getting-started.md).
+
+Once you've made your changes, update the snapshot files such that they reflect the updated state of the data
+```bash
+pytest --snapshot-update
+```
+
+Finally, submit a pull request with a clear description of your changes and the sources you used for verification.
+
+## Code Style and Best Practices
+
+- Follow PEP 8 style guidelines
+- Write clear, descriptive docstrings using Google-style format
+- Keep your changes focused and well-documented
+
+Thank you for helping to maintain accurate holiday data for Holidata!

README.md

@@ -62,7 +62,7 @@ There is also no explicit representation of partial holidays.
 
 ## Contributing
 
-If you'd like to contribute to holidata by adding support for a new country or updating existing implementations, see [the how-to guides](docs/how-tos/getting-started.md) for further instructions.
+Take a look at [CONTRIBUTING.md](CONTRIBUTING.md) on how you can contribute. ❤️
 
 ## License