You found something broken, some missing translation or you want to discuss anything? open an issue
You want to contribute 😍? Awesome! Head over to the issues section, choose one you like and ask whether you can pick it up.
All contributions either bugfixes or new features should be worked on their own branches. To do that start a new branch from master and open a pull request against it when you are done. Are you new to this? Read Bitbucket's documentation about Feature Branch Workflow.
Once the pull request gets approved it will get merged into master and this will trigger a deploy to Github pages, so the changes will be live 🎉.