ENH MutliLinkField sorting

[emteknetnz]

Issue #139

react-dnd -> dndkit

Most recent version of react-dnd is 16 which was released in Aug 2022 (we're still using version 5 on elemental), it failed to work at all in our setup

• I followed the basic "quick start" instructions and got a console warning
• Jest failed to work, complained about an 'Unexected export token' in a react-dnd file. Apparently it uses the wrong JS syntax for our setup.
• Looking around some github comments it seems like the export issue started with version 16, it wasn't a problem with version 15

I've opted to use https://docs.dndkit.com/ instead which seems to work well and had its last release in Nov 2023

Screen jumping on sort

The screen jumps on sort, though it also does this on anything that causes a re-render e.g. link edit. I've created a new issue for this. #169

Hover/focus styling

Styling for the LinkField hover/active/focus states is generally poor, I've created a new issue to tidy this up #168

Design review

Design team has reviewed and approved with understanding the screen jumping and hover/focus styling will be handled separately

[GuySartorelli]

The bottom border of the last item in the list is missing:
Before:

This PR:

[GuySartorelli]

I took this after rebasing so I don't have the scroll popping issue.

Screencast.from.16-01-24.10.00.44.webm

There are two issues here.

Flickering

I think we shouldn't bother trying to show the loading component here because that flickering is just very visually distracting and doesn't have any clear benefit.

At some point that decision looks like it was made for elemental as well, because elemental doesn't show the loading component when sorting.

Briefly rendered in the wrong order

Very briefly after letting go of the item I'm dragging, it pops back into its original position, and then pops into its new position after loading.

We should immediately render it in its new position after dropping, and only pop it back to its original position if something goes wrong with the network request to save the new sort order.

[GuySartorelli]

Also needs rebase please

[GuySartorelli]

The actual sorting works really well now - I like that it's constrained to the parent and the vertical axis.

But now when I add new links, they don't appear until I refresh the page:
Screencast from 17-01-24 15:03:47.webm

[GuySartorelli]

Looks great, works well locally.