AVIF support: filters to manage images formats to generate

[Tabrisrp]

Scope a solution ✅

• Add a new filter imagify_nextgen_images_formats, with an array containing the next-gen images formats to generate
• Use this filter in a method to get the image formats to generate, that can be re-used where necessary
• This method will by default use the WebP value, replaced by AVIF if enabled in the UI
• Modifying the filter value will allow to either generate both formats, or none of them

Estimate the effort ✅

Effort [S]