packagist: resources not loaded due to content-security policy

It’s not a big issue, but images linked in GitHub readme files don’t load giving a console error

rfc1867:1 Refused to load the image 'https://raw.github.com/Lewiscowles1986/rfc1867/HEAD/diagram/class-relationship.png?raw=true' because it violates the following Content Security Policy directive: "img-src 'self' https://www.gravatar.com/ https://camo.githubusercontent.com/ https://ssl.google-analytics.com/ http://www.google-analytics.com/".