Shared UI Components across platform

[zdmc23]

I propose leveraging Expo or Ionic to develop Shared UI components (Custom Field Types, Tiles, Custom Post Types), which would consolidate testing efforts, and would also ease any transition toward PWA or a "headless" D.T. (These components would be in React, so we will be able to reuse existing code).

Ref: DiscipleTools/disciple-tools-mobile-app#540

[mikeallbutt]

I support this idea if it will make DT be more easily developed and used by more people.