Simulator iframe breaks under embedder crossOriginIsolated (COOP/COEP)

[dev-clemons]

We embed the simulator in our web app (webtigerpython.ethz.ch). Our app needs
crossOriginIsolated for SharedArrayBuffer, and once that's turned on,
the simulator iframe stops working it sends no
Cross-Origin-Resource-Policy/COOP/COEP headers of its own, so it gets
blocked as a nested cross-origin frame.
Could you add Cross-Origin-Resource-Policy: cross-origin (and if possible
COOP/COEP too) to simulator.html and its subresources?