Flexible block editor for single event pages#18

Proposal to redesign the Single Event page, taking advantage of the Block Editor, preparing for Full Site Editor support, and improving event-creation UX. (Migrated from featureOS: https://the-events-calendar.featureos.app/p/event-single-redesign)

This feature would re-design our existing event blocks to provide much flexibility and customization. This would also improve the default design of the event single page. Additional features could include having re-usable block templates that apply events automatically.