DEV: adds server:after-body-open (PR #14106)

This change is to allow to add a node at the top of body. This is currently done through DOM in a plugin which is causing a full Recalculate Style.


I took a quick peek at build_plugin_html and it seems to check allow_plugins? already, so this if statement shouldn’t be necessary.

Yes I got the same question actually, I saw we are doing it at other places, but I also think we could drop it everywhere, can do it in a separate PR if you want.

We probably should! I’ll approve this now, though. Thanks!