Is using a web browser really necessary for viewing Markdown? Seems a really inefficient way to view a what's supposed to be a small and minimal language.
By the way, while browsers can be both CPU and memory hogs, they're not inherently inneficient and it mostly depends on what the website is doing. This project uses minimal JavaScript and no frameworks, and while I didn't measure it I assume this site should be reasonably efficient, both in memory and CPU usage.