create 'Data' menu item

As requested by Lemoness via Alys in Aspiring Coders:
>On the website, we want a new menu item called "Data" in between "Inventory" and "Help". It should have two entries under it: "Data Display Tool" and "Export Data". The top-level "Data" item and the "Data Display Tool" entry should both point to http://data.habitrpg.com and that page must open in a new window/tab. The "Export Data" entry should point to https://habitrpg.com/#/options/settings/export and open in the tab that the user is already on.

New /en/ definitions in https://github.com/HabitRPG/habitrpg-shared/pull/357