cdnjs is a free distributed JS library delivery service.
Cloudflare is a web-infrastructure and website-security company, providing content-delivery-network services, DDoS mitigation, Internet security, and distributed domain-name-server services.
Heroku is a cloud platform as a service (PaaS) supporting several programming languages.
Next.js is a React framework for developing single page Javascript applications.
Priority Hints exposes a mechanism for developers to signal a relative priority for browsers to consider when fetching resources.