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+# Contributing
+
+## Code style
+
+* Make sure your code follows the [PSR-12](https://www.php-fig.org/psr/psr-12/) code style.
+You may use `composer run phpcs` to verify that.
+* Use `use` statements wherever possible instead of writing the fully qualified name.
+* Order the composer/npm dependencies alphabetically.
+* Do not use code from the [includes](./includes) directory anywhere else.
+* If possible cover your code by test cases.