Progressive JPEG transcoding?

[julianrubisch]

Is it possible to supply a configuration option that will allow to use imagemin-jpegtran's progressive option?

https://github.com/imagemin/imagemin-jpegtran

I'll gladly supply a PR if you concur!

[BezPowell]

I'd also really like this feature. Currently Zola doesn't support encoding jpegs as progressive and this plugin being able to re-encode jpegs to progressive would be invaluable.