Change CKEditor ResourceLink plugin attribute name

[ChristopherChudzicki]

Our ResourceLink plugin for CKEditor relies on HTML anchor tags having a data-uuid attribute. The attribute value previously was a uuid. It is no longer a UUID, but rather some string encoding encoding (1) a uuid and (2) possibly some other information.

We use a single attribute to pass this data to CKEditor because that's most convenient as far as CKEditor is concerned

Suggested new name: data-link-attrs.

See discussion at #1036 (comment)

[alicewriteswrongs]

In order to change this we'll need to make a change over in https://github.com/mitodl/ckeditor5 and publish a new version of our forked package (https://www.npmjs.com/package/@mitodl/ckeditor5-resource-link) which has the change. The change should be just changing a constant value.

Then once we have that released, we can introduce a PR in Studio to update to the new package and make the necessary changed to our ResourceLinkMarkdownSyntax plugin (which, again, will be basically just changing one constant value)