[feat] Move adjacent windows together in a window group

Related:
- #568

Example: https://www.nurgo-software.com/products/aquasnap#:~:text=Move%20windows%20together

Motivation: With support for dynamic grouping of windows along their shared borders or corners, it becomes natural to allow moving all grouped windows together, to maintain the shared borders and corners. This is a very useful feature that I miss from using AquaSnap on Windows, and for a long time was a major reason why I continued to use Windows. I'm not aware of any other window managers that have a feature like this, and it's a game changer.