Shouldn't `InstallEvent` has a constructor?

[skyclouds2001]

current the definition for InstallEvent does not has a constructor, this is different from other event interfaces and is quite uncommon, should it also define with a constructor, too?

relates with mdn/browser-compat-data#22870

[skyclouds2001]

but interestingly, in browser implement InstallEvent is constructible

test in https://worker-playground.glitch.me/

[mkruisselbrink]

Yes, I believe this is an oversight in the spec that was missed when InstallEvent was added in #1701. I can't think of any reason why we shouldn't have a constructor.