sources: don't escape Unicode characters in tag search URLs.

Fix it so that Unicode characters aren't unnecessarily percent-encoded when generating tag search
URLs. For example, generate URLs like this:

* https://www.pixiv.net/tags/オリジナル/artworks

Not like this:

* https://www.pixiv.net/tags/%E3%82%AA%E3%83%AA%E3%82%B8%E3%83%8A%E3%83%AB/artworks

app/logical/source/extractor/art_station.rb

@@ -48,7 +48,7 @@ class Source::Extractor
 
     def tags
       api_response[:tags].to_a.map do |tag|
-        [tag, "https://www.artstation.com/search?q=#{CGI.escape(tag)}"]
+        [tag, "https://www.artstation.com/search?q=#{Danbooru::URL.escape(tag)}"]
       end
     end