[FEATURE REQUEST] Responsive Background Images

Hi Miles,

Thank you very much for this great plugin.
I have an idea to make the plugin even better.
Currently, it is possible to give a container a background image.
This image is displayed on all devices in the same way. This leads to performance losses on mobile devices, especially with large images, as they have to render a significantly larger image.

So here are my ideas:

1. Couldn’t we use one image per breakpoint?
   It is already possible to hide the background image per breakpoint, so what if this option was simply expanded? If a background image is available per breakpoint, it would simply have to be written to the head of the current page in a style block using media-breakpoint-up().
2. And this is now a really advanced idea:
   What if you have the option of cropping the uploaded background image for each breakpoint? This is then automatically stored next to the original image used with the PageID and the breakpoint in the file system and then used for each breakpoint like in the idea above.
   I only came up with this idea because Typo3 already supports something like this. A simplified form (without fixed ratios) would already be a great feature, wouldn’t it?

I hope you like my ideas and thank you for reading.

Best,
Matt