Make tags sortable with drag&drop

Feature that enables sorting of tags by drag & drop.

To merge with [HabitRPG-shared/#276](https://github.com/HabitRPG/habitrpg-shared/pull/276).
I see. K, per https://github.com/HabitRPG/habitrpg/commit/50a34eb6c70cd8f042731a4d6925c023803de4dd#commitcomment-7448834 no longer necessary