integrate legacy yt xml subscription import with new json sub import

src/invidious.cr

@@ -760,11 +760,17 @@ post "/data_control" do |env|
           end
         end
       when "import_youtube"
+        if body[0..4] == "<opml" 
+          subscriptions = XML.parse(body)
+          user.subscriptions += subscriptions.xpath_nodes(%q(//outline[@type="rss"])).map do |channel|
+            channel["xmlUrl"].match(/UC[a-zA-Z0-9_-]{22}/).not_nil![0]
+          end
+        else
           subscriptions = JSON.parse(body)
-
           user.subscriptions += subscriptions.as_a.compact_map do |entry|
             entry["snippet"]["resourceId"]["channelId"].as_s
         end
+        end
         user.subscriptions.uniq!
 
         user.subscriptions = get_batch_channels(user.subscriptions, PG_DB, false, false)