Add line breaks to fix header formatting etc
Created by: rudibs
See rendered markdown at https://github.com/rudibs/Sia/blob/rudi-fix-contributing-doc-formatting/doc/Guide%20to%20Contributing%20to%20Sia.md
Created by: rudibs
See rendered markdown at https://github.com/rudibs/Sia/blob/rudi-fix-contributing-doc-formatting/doc/Guide%20to%20Contributing%20to%20Sia.md