Figure out where the (missing) Delete buttion will go in the BSS design

[enjoysmath]

I forgot to add in the Delete button (see quiver core: https://q.uiver.app) in the BSS design.

Remember, we don't want any more than 6-8 buttons on the toolbar, because the users on an iPhone or smaller need some button room to be able to press the button accurately. So, rearrange "Share" dropdown into a submenu to make room, for example.

Delete should probably be a top-level thing, because it's a very common edit operation.