I’ve been messing about with various visualisation using D3 and leaflet. These tools are great but they interact with a browser and you will want to check your code before sending it to a Gist so that it can be rendered on Bl.ocks.
The links have all the documentation for doing so.
Once you have that installed, you simply navigate to your folder with your website in either a terminal or powershell, and type
http-server. When you are finished, type