Cross-origin isolation in a Firefox extension

Question

In Chrome, one can make an extension cross-origin isolated by adding the following to manifest.json:

{
    ...
    "cross_origin_embedder_policy": {
        "value": "require-corp"
    },
    "cross_origin_opener_policy": {
        "value": "same-origin"
    },
    ...
}

However, this is not supported on Firefox. I need to use SharedArrayBuffer, so I need cross-origin isolation. How do I make an extension cross-origin isolated on Firefox?