fix: distinction between update:layout and layout-updated events

[schuhwerk]

Hi! Thanks for your great work!

I just updated this PR with your most recent changes (and cleaned things that did not belong in here).

I came across the issue, that you don't make a distinction between an ongoing layout change and a finished one here. In both cases the update:layout event is emitted.

So I gave the second one (in the highlighted lines) a different name and based the naming of the finished event (layout-updated) on the implementation of jbaysolutions.

I'm not sure why they used different notations ( "-" vs ":" )... What do you think?