Create keyboard shortcut for `Hide tabs and sidebar`

[deweesevs]

I understand that a command for collapsing and expanding the sidebar was implemented with this. However, this still forces users to see the tab favicons. I think the ability to toggle Sidebar:HideTabsAndSidebar with a keyboard shortcut, to fully hide and display the favicons [and tab names, if expanded] would be useful.

[Jon]

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