Add an option to keep outline open

[LukasDrude]

The outline is fantastic. But it keeps disappearing, when I click onto the page content itself.

I use it for Jupyter Notebooks, where you easily get lost on large pages.

I would be happy about adding an option, or simply keeping the popup open until one clicks on the h5o icon again.

[liango2]

yes, i need this feature too

[lotosbin]

sidebar will be better