Add translations strings for impersonate user feature.

Thanks to xet7 !

i18n/en.i18n.json

@@ -359,6 +359,7 @@
   "headerBarCreateBoardPopup-title": "Create Board",
   "home": "Home",
   "import": "Import",
+  "impersonate-user": "Impersonate user",
   "link": "Link",
   "import-board": "import board",
   "import-board-c": "Import board",
@@ -403,6 +404,7 @@
   "list-select-cards": "Select all cards in this list",
   "set-color-list": "Set Color",
   "listActionPopup-title": "List Actions",
+  "settingsUserPopup-title": "User Settings",
   "swimlaneActionPopup-title": "Swimlane Actions",
   "swimlaneAddPopup-title": "Add a Swimlane below",
   "listImportCardPopup-title": "Import a Trello card",