Implement enhanced column manipulation functionality

[pydsigner]

Let me know what you think about this. It replaces the current tweak-based column management with overlays for moving, inserting, and deleting columns. I think it's a more natural approach. As it stands, it needs some visual work, but I wanted to get it in front of you and see what you think of the concept. Here's a screenshot of the updated demo:

[pydsigner]

I tried doing the movement with SortableJS but there's a whole bunch of jank with the interactions among the different editorJS instances so I bailed on that...

[calumk]

Hmm.
I like the drag/drop idea.

I use https://github.com/kommitters/editorjs-drag-drop with some of my projects, but that has just been end-of-life so I wonder if there is a way of building a whole new drag-drop plugin that also supports the columns....

[pydsigner]

I can try merging your event propagation changes in and see if that makes the DnD work better. The problem I was seeing is that the built-in drag-and-drop behavior of EditorJS was firing along with the SortableJS event and breaking everything. I was having a hard time finding where I could stop those propagations.