Add switch to collapse/expand sidebar

[exalate-issue-sync]

Userstories

As a user I want to be able to expand the sidebar even if no resource is selected for that I can execute actions for the current folder I am in.
As a user I want to be able to collapse the sidebar for that it doesn't clutter the view if it's not desired.

GitHub ticket - #2061 and #3919

AC:

• on click on the switch, the sidebar opens / closes;
• the switch visuallizes the current state (expanded / collapse)
• if no resource is selected, the current parent is the selected resource in the sidebar
• if the current folder is root, "Select a file or folder to view details." is displayed with a nice icon in the sidebar (icon: https://materialdesignicons.com/icon/cursor-default-click-outline)
• action "open folder" is not avialable if no resource is selected (is already fixed because we select a resource on rightclick)
• actions copy/move/delete need to turn into batch actions when multiple resources are selected, other actions should disappear
• having multiple resources selected, people, links and version disappear (already done)
• tests

[~tbaader]add scribbles with only icons (no text)