When I was investigating setting up Trello Power ups (https://gitlab.com/gitlab-org/gitlab-ce/issues/32042) using gitlab pages, I realized that I wasn't able to use gitlab pages because CORS was not enabled ``` XMLHttpRequest cannot load https://[redacted].gitlab.io/trello-power-up/manifest.json. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'https://trello.com' is therefore not allowed access. ``` Considering how GitHub pages allows all origins, we should do the same. ``` HTTP/1.1 200 OK Server: GitHub.com Date: Thu, 08 Jun 2017 19:09:56 GMT Content-Type: text/html; charset=utf-8 Content-Length: 56130 Last-Modified: Tue, 02 May 2017 09:38:20 GMT Access-Control-Allow-Origin: * Expires: Thu, 08 Jun 2017 19:19:56 GMT Cache-Control: max-age=600 Accept-Ranges: bytes X-GitHub-Request-Id: FEC6:1B600:DC488E:1238FD8:5939A104 ```