Depends what you mean by that precisely. But you can load things from cloudflare's ipfs gateway without doing anything special otherwise. Directly from ipfs - not without extensions.
A PWA with a Service Worker could perhaps implement its own client-side "gateway", translating public gateway URLs into direct IPFS access. Without the Service Worker (or without JS) it would fall back to using the gateway.
It sounds like we'd need to have browsers implement IPFS protocol support directly for this to be a feasible alternative to centralized CDNs.