Now I have a simple blog platform using Jekyll & GitHub Pages, I need to see whether anyone is looking at it!
Google Analytics is super simple to add to Jekyll site. Jump over to https://analytics.google.com/ sign up for a free Analytics account, then create a new Property (Website to track). Copy the Tracking ID (in the form UA-XXXXXXXX-X) and copy into your _config.yml file:
# Enter your Google Analytics web tracking code to activate tracking google_analytics: UA-XXXXXXXX-X
Google Tag Manager
Google Tag Manager is just slightly more involved to setup.