feat: improve change editor menu keyboard navigation (#831)

app/assets/javascripts/views/constants.ts

@@ -1,6 +1,11 @@
 export const PANEL_NAME_NOTES = 'notes';
 export const PANEL_NAME_NAVIGATION = 'navigation';
+
 export const EMAIL_REGEX =
   /^([a-zA-Z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-zA-Z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?\.)+[a-zA-Z0-9](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?)$/;
+
 export const MENU_MARGIN_FROM_APP_BORDER = 5;
 export const MAX_MENU_SIZE_MULTIPLIER = 30;
+
+export const FOCUSABLE_BUT_NOT_TABBABLE = -1;
+export const NOTES_LIST_SCROLL_THRESHOLD = 200;