Roadmap app global constants

ee/app/assets/javascripts/roadmap/constants.js

+export const TIMEFRAME_LENGTH = 6;
+
+export const EPIC_DETAILS_CELL_WIDTH = 320;
+
+export const TIMELINE_CELL_MIN_WIDTH = 180;
+
+export const SCROLL_BAR_SIZE = 15;
+
+export const TIMELINE_END_OFFSET_HALF = 17;
+
+export const TIMELINE_END_OFFSET_FULL = 26;