adding a SubToMe button for easier following as RSS is had to deal with

Adding a [SubToMe](https://www.subtome.com/#/) button. RSS is amazing but is hard to use for non-geeks as it requires them to copy paste URLs which is both complex and counter-intuitive. Also, it does not work on mobile/tablets. SubToMe is just an HTML5-powered button to make that easy and does not "break" the RSS decentralization and beauty!