cdnjs is a free distributed JS library delivery service.
Gatsby is a React-based open-source framework with performance, scalability and security built-in.
Google Analytics is a free web analytics service that tracks and reports website traffic.
Google Tag Manager is a tag management system (TMS) that allows you to quickly and easily update measurement codes and related code fragments collectively known as tags on your website or mobile app.
Handlebars is a JavaScript library used to create reusable webpage templates.
A modest JavaScript framework for the HTML you already have.