Scaffold a Lit web component for the form builder

[spwoodcock]

• Create a Lit component that is a wrapper for lower level fields.
• In a similar vein to ODK web-forms, where they have a wrapper OdkWebForm component, then many underlying components designed that can slot inside the parent component.
• The component should be designed to accept many 'slot' components, in a dynamic nature - rendering input components as they are drag-and-drop'd in the interface. Related to Research ways to implement a drag-and-drop interface on the underlying web-component #6.