cdnjs is a free distributed JS library delivery service.
Firebase is a Google-backed application development software that enables developers to develop iOS, Android and Web apps.
HTTP Strict Transport Security (HSTS) informs browsers that the site should only be accessed using HTTPS.
HTTP/3 is the third major version of the Hypertext Transfer Protocol used to exchange information on the World Wide Web.
Materialize CSS is a front-end framework that helps developers create responsive and mobile-first web applications. It is based on Google's Material Design guidelines.