Main UI & screen navigation 🧭

[opatry]

Something close to the Reply compose sample is expected.

• [x] Theming (Primary color #81FFDE, dark background #023232)
• [x] Master/detail
  • [x] Empty state for task lists in master pane
  • [x] Empty state for selected list in detail pane
  • [x] Master contains task lists
  • [x] Detail contains tasks of the selected list
  • [x] Selected a task might open details in a bottom sheet or a dialog
• [x] FAB to create a new task
  • [x] Open dialog to fill task detail (allowing to choose target list with a drop down)