shareable url for achievements

[kkuepper]

• example urls
  • /achievement/GibraltarOneWeek
  • /achievement/romantoplistener
• apple-app-site-association has already been updated: /achievement/*
• 95% of cases the achievement will be in the project box on the homescreen
• you can load a single achievement via /statistics/achievement/{id}?theme=dark (make sure to provide the theme as well)