For us to accept contributions the addition has to be a reasonable implementation of new functionality.
Implementations of new functionality require all unit tests to run without failures
as well as unit tests covering your functionality.
To run unit tests execute vendor/bin/phpunit from the project's root directory.
Before opening a pull request have a look at existing issues to see if the topic is already covered. If you are unsure about opening a pull request consider opening an issue.
Keep your master branch up to date (see Git help).