Add new 'top' docking area to display content above main content

[danielwiehl]

Currently, parts can be docked on the left, right, and bottom sides, but not on the top side.

The workbench should support a new docking area 'top' to display content above the main content.

Requirements:

• Add a new docking area named top to allow parts to be docked above the main content.
• The top docking area is always placed between the left and right docked parts. Panel alignment settings do not affect the alignment of the top docking area.
• The top docking area is a single area; unlike the bottom docking area, it cannot be split into left and right areas.
• Activity items for opening and closing the top docking area are placed in the right sidebar, displayed before the activity items for right-top and right-bottom, separated by a divider. A maximum of three groups can appear at the top of the right sidebar, in this order: top | right-top | right-bottom.

[Marcarrian]

Consider implementing similar to other docking areas: Two new docking areas top-left and top-right to allow for full flexibility.