Bootstrap v4 dark mode for modals and settings window (#1650)

* Bootstrap v4 dark mode for modals and settings window

* Fix package-lock.json

* Fix package-lock.json again

* Merge'd

* Oops

* Refactor into helper

src/common/communication.ts

@@ -20,6 +20,7 @@ export const EMIT_CONFIGURATION = 'emit-configuration';
 
 export const UPDATE_TEAMS = 'update-teams';
 export const DARK_MODE_CHANGE = 'dark_mode_change';
+export const GET_DARK_MODE = 'get-dark-mode';
 export const USER_ACTIVITY_UPDATE = 'user-activity-update';
 
 export const LOAD_RETRY = 'load_retry';