Feature: Refactor lightbox to generate slides dynamically and refine web componentry

[cbutcosk]

This PR (along with thegetty/quire-starter-default#45) refactor the q-lightbox element:

• Improves subcomponent composition with four named slot elements for data, ui, slides, and styles
• Compiles lightbox styles and inserts them in the component's style slot at build-time
• Generates slides dynamically at component startup from JSON