a tiling window manager for X11

Changes for 2.0 - 2023-10-26

• Implemented tag_append() -- it's possible to append windows from other tags to the active one.
• xcb_unmap_window() was removed. From now on the windows are being moved out of visible area instead of unmap.
• Make initial_pointer_position multiple screen-aware: mouse pointer can now warp to the central screen.
• Other minor improvements: