Add download for articles

app/controllers/articles_controller.rb

@@ -21,6 +21,12 @@ class ArticlesController < ApplicationController
     end
 
     @articles = Article.undeleted.where(supplier_id: @supplier, :type => nil).includes(:article_category).order(sort)
+
+    if request.format.csv?
+      send_data ArticlesCsv.new(@articles, encoding: 'utf-8').to_csv, filename: 'articles.csv', type: 'text/csv'
+      return
+    end
+
     @articles = @articles.where('articles.name LIKE ?', "%#{params[:query]}%") unless params[:query].nil?
 
     @articles = @articles.page(params[:page]).per(@per_page)