Make the Admin left sidebar collapsible

[smustgrave]

Would like to make the left sidebar collapsible to free up some space.

[carwin]

This is a nice idea but we might try to figure out a way to turn this into an option that users can enable or disable since it isn't part of the original Lark designs.

[carwin]

We talked about this on the phone with our designer. The follow-up task on the development end is to add a theme settings option to give the ability to turn the collapse feature on and off.

We'll await designs for how to address the Shortcuts feature and icons when the menu is collapsed.