Add official logo to simpleicons.org

[rickstaa]

Maybe it is an idea to add the official Gitcoin SVG logo to the https://simpleicons.org project. Doing this allows users to create shields.io badges in their GitHub Readme easily. I found the information needed to make such a request on https://gitcoin.co/press, but I think it is best somebody from the organization submits the request. The request can be made at https://github.com/simple-icons/simple-icons/issues/new?assignees=&labels=new+icon&template=icon_request.yml.