Add support for multi-resolution mobile/desktop images (srcset)

[gcushen]

Feature Request

Goal:

Speed up page loads and improve Lighthouse scores by loading images dynamically depending on the screen size.

Scope

blox-tailwind module

Actions:

Add srcset for multi-resolution mobile/desktop images (whilst also checking all images utilise native lazy loading).

Add srcset to the following images:

• [ ] Blocks with image functionality
• [x] Images/Figures
• [ ] Images in Listing Views (list items)
• [ ] Featured/Cover image
• [ ] Header image
• [ ] Block background images
• [ ] Gallery images (not yet ported to Tailwind module)

[jwmbeenakker]

I think this especially important for the block background images, as these are also part of hero-block and therefore significantly impact the loading times of the homepage...