FEATURE: Handle Youtube RSS feeds (#24)

app/models/discourse_rss_polling/feed_item.rb

@@ -19,6 +19,8 @@ def content
         break if content = @accessor.element_content(tag_name)
       end
 
+      return youtube_embed if is_youtube?
+
       content&.force_encoding('UTF-8')&.scrub
     end
 
@@ -45,5 +47,15 @@ def categories
     def url?(link)
       link.present? && link =~ /^https?\:\/\//
     end
+
+    def is_youtube?
+      url&.starts_with?('https://www.youtube.com/watch')
+    end
+
+    def youtube_embed
+      <<~POSTCONTENT
+        <div><iframe width="#{SiteSetting.max_image_width}" height="#{(SiteSetting.max_image_width / (16.0 / 9)).to_i}" src="https://www.youtube.com/embed/#{@accessor.element_content(:id).split(':').last}" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe></div>
+      POSTCONTENT
+    end
   end
 end