Add : feed icon to rss2.xml
Add : feed icon to rss2.xml

I configured `feed.icon` in the `config.yml` file but that icon was not exposed when creating the feed xml file.
So, I Add in rss2.xml `<url> {{(url + config.feed.icon) | uriencode}} </ url>` and I see that it works.
hexojs/hexo-generator-feed