Add general image gallery to form system

Quite often we need an image or images to represent someone or something, like an image in a contacts card, or a screenshot of an app in an app store, or a picture of a product in a catalog, or also background photos for profiles, projects, etc.

When the image is added, it can be be, ideally

• Take n as a picture with the camera
• uploaded as any file
• dragged in from anywhere in solid
• draged from a desktop file
• dragged from the web (when permitted in browser)
• selected from one's photos (esp on mobile)
• Selected from one of ones solid photo libraries

(Obviously circular methods would not be used -- not selected from a photo library to be put in a photo library.)

• We have code to do this in the contacts
• Many UI frameworks have picture input APIs we can use

Like colors, pictures allow users to customize things.
Let's make it easy for devs to make it easy for users to add pictures to anything
Let's add picture input and gallery view as form type in the form system.

Start by reading the existing contacts image code and the form system, then compare them with picture-input APIs from relevant UI frameworks. Define how the requested picture input and gallery form types should cover camera, uploads, drag-and-drop, photos, and photo libraries; the work is done when those form types support the stated image use cases.