Add multipliers for image sizes for different pixel ratios
In addition to the various image sizes defined for resizing images this could be used to create larger additional copies for high-resolution screens with different pixel ratios as used on mobile phones, tablets and modern desktop computers and laptops. The images could use a suffix to the filename which shows the pixel ratio they are targeted at (e.g. image.jpg and image@2x.jpg). The multipliers could be defined in a similar way as additional image sizes in the web.config file.
