Fix relative SVG rendering

[ioquatix]

As discussed in isaacs/github#316

Essentially embedding SVG images into a README.md file doesn't work but probably should. It's apparently broken due to the content type being incorrect for the SVG file being served.

[gustavomdsantos]

+1

[derekstavis]

👍

[FranklinYu]

👍

[klorenz]

+1

👍

[dangnelson]

Wow, has this really been a bug for over a year?

[FranklinYu]

@dangnelson No, I don't think they even regard it as an issue. This is probably a "won't fix".

[kivikakk]

This isn't an issue with the Markup gem itself, but it certainly is a valid bug. Looking into a resolution now.

[ioquatix]

@kivikakk any update? Thanks!!

[kivikakk]

@ioquatix: we're discussing it currently! The biggest issue we need to overcome is security due to JS execution in SVG — allowing user-controlled scripts on a GitHub domain could be dangerous — so we're considering strategies to work in out. It might take a bit to get it fully ironed out, but I'm pushing this forward internally, so I'll let you know when there's any updates.

[ioquatix]

@kivikakk I thought that might be a problem. I'm glad you are thinking about it. The content is served from a raw.github.io right? What about using something like https://content-security-policy.com to protect your main domain?