Custom CSS is injected too late #4312

Also I'd replace elementReady('body') with a custom awaiter like:

while (!document.body) {
    await Promise.race([new Promise(setTimeout), new Promise(requestAnimationFrame)])
}

This is because elementReady only uses requestAnimationFrame, so nothing is run until the user switches to the tab. This means that every time you switch to the tab, there's a FOUC or delay because RG will run at that point.