The best way to contribute is to simply make an issue and fill in the necessary information for the selected template.
If instead of creating an issue you decide to open a pull request, please modify only the source.scss file (unless bumping the version). Before opening a PR, make sure you compile your changes by running npm run compile. (You may also run npm run watch before making any changes to automatically compile every time you save.) Icons should be made in 24 x 24 containers.
Be fully prepared for any submitted pull requests to be heavily critiqued or denied. If I think any icons you add or change are out of place or plain ugly, I will deny your pull request. If you failed to format your code to my liking, I will try my best to work with you to fix it.
Thank you for your contribution!