Add an iso setting for disabling the document outline in the List View

[carolinan]

Make it possible to disable the document outline in the list view by setting it to true or false in applyDefaultSettings.
Add a condition to ListViewSidebar that enables or disables the document outline based on this setting.

My use case: I use an isolated block editor to demo single blocks, and I want to hide the document outline to reduce noice.
I can do this locally in my own project, but it might benefit others too.