Implemented several GUI parts

client/package-lock.json

client/package.json

client/public/locales/de/translation.json

client/public/locales/en/translation.json

client/src/Router.tsx

client/src/components/ManagedBoatTile.tsx

client/src/components/Modal.tsx

client/src/components/RentedBoatTile.tsx

client/src/components/StaffLayout.tsx

client/src/components/StaffModal.tsx

client/src/components/UserLayout.tsx

client/src/components/forms/BoatInfo.tsx

client/src/components/forms/EditBoatTypeForm.tsx

client/src/components/forms/EditSports.tsx

client/src/components/layout/Divider.tsx

client/src/components/layout/Loading.tsx

client/src/index.tsx

client/src/pages/public/BookingForm.tsx

client/src/pages/public/BookingSignOutSuccess.tsx

client/src/pages/public/BookingSuccessful.tsx