cdnjs is a free distributed JS library delivery service.
D3.js is a JavaScript library for producing dynamic, interactive data visualisations in web browsers.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
Netlify providers hosting and server-less backend services for web applications and static websites.
Open Graph is a protocol that is used to integrate any web page into the social graph.
Unpkg is a content delivery network for everything on npm.