Added calendar heatmap visualization

While I was finalizing the /changelog page I was thinking about how cool it would be to add some sort of a data visualization because… I <3 data vis. So, the first thing that bumped into my head was a calendar heatmap like the one on the GitHub profiles for activity. Lurking around the internet I found this amazing library called Cal-Heatmap which does exactly what I wanted.

It took some time to implement it, it’s not very straightforward if you want it to be responsive and I found some bugs but the end result is amazing! Check it out on the /changelog page.