Custom metadata/fields attached to assets/images

As it stands, when you upload a file to the asset library you can change its name and what folder it resides in. What we cannot currently do is attach other information such as alt-text (important for accessibility and SEO), or any other metadata about the asset. Another use-case that having this would solve is generating a blurhash/plaiceholder string on upload (or during static page generation) and storing that alongside the asset to be used going forward.