Dynamically add workspaces to the left

## Problem

Sometimes when I'm on the first/left-most workspace, I want to make a new workspace to the left to aid my mental/spatial model. But if I'm on the left-most workspace, that's not currently easy.

## Proposal

It would be neat if I could just swipe over to a new workspace to the left. Under the hood this might need to actually move all windows to the right one workspace, but to the user, it should feel like making a new workspace to the left (just like dynamic workspaces to the right). Ideally this would also work with moving windows with keyboard shortcuts/window context menu as well.

## Prior Art

We sort of half support this in the Multitasking View, but only when dragging an app's icon on the workspace thumbnails at the bottom of the overview. GNOME Shell supports this for moving a window above the top-most workspace; they seamlessly move all other windows down one workspace.