Serve Images in a next-gen format

[davidbeig]

Currently the images provided by users are served by goteo in the same format as they were given. This makes us serve images in png and jpeg formats without limits in their size.

With the formats we are currently using we can see, through PageSpeed, that we are serving around 10mb of data related to images.

I propose to change the format we use to serve images to Webp and AVIF if it's accepted by the browser.

Also i think this is the next necessary improvement since the use of lazy and picture to handle the different images sizes in the home of Goteo.