[ENG-235] Create DG summoning menu (#169)

* [ENG-259] Create Observer and UI pattern (#138)

* create event listener for @ key

* fix ui

* address PR comments

* cur progress

* current progress

* tested yayyy

* add the checkbox UI

* fix focus issue

* rm logs

* address PR comments

* address PR comments

* [ENG-261] Query function for DG summoning menu (#150)

* cur progress

* current progress

* rm logs

* address PR comments

* address PR comments

* query works

* address PR comments

* address PR comments

* sm change

* [ENG-299] Trigger setting for DG summoning menu (#162)

* setting menu done

* trigger works correctly

* clean up

* address PR comment

* optimize getFocusedBlock()

* address nit comments

* fix bug (#166)

* address PR comments

Author: trangdoan982