I want to add flexibility polyfill in my build to support ie8 & 9. Is there a way with gulp to add in the -js-display: flex; before display: flex; as required?
.container {
    -js-display: flex;
    display: flex;
}
https://github.com/10up/flexibility
Thanks!
                        
You can use
gulp-postcssin combination with thepostcss-flexibilityplugin: