library: add Overlay Split View entry

[halfmexican]

Fixes #406

[sonnyp]

The window is too small and the sidebar should automatically show/hide depending on the window width.

Could you replicate exactly the "Adwaita Demo" example ?

I think it's what users want in 99% of cases.

[halfmexican]

overlay.webm
The automatic hiding of the sidebar appears to work for me.

[sonnyp]

There were conflicts and unwanted changes in the diff.

I fixed it and merged main into your branch, please git pull.

So I don't know what's going on but here I get the following now:

Screencast.from.2023-08-09.21-09-20.webm

Are you using the same method as "Adwaita Demo" to set the window size?

[sonnyp]

Is this ready for review?

[halfmexican]

Yes, I thought I forgot the tooltip text but it appears I did included that

[sonnyp]

Nice.

I removed modal: true because without set_transient_for it feels buggy.

(Can't interact with Workbench window but there is no feedback as to why)