タグ・グループを Wiki から分離 (#425) (#429)

Reviewed-on: #429
Co-authored-by: miteruzo <miteruzo@naver.com>

backend/config/routes.rb

@@ -1,4 +1,6 @@
 Rails.application.routes.draw do
+  resources :tag_groups, only: [:index, :show, :create, :update]
+
   resources :nico_tags, path: 'tags/nico', only: [:index, :show, :update]
 
   scope 'tags/:parent_id/children', controller: :tag_children do