insertdelta is always a string in Y.Text. Furthermore, Y.Text also allows assigning formatting attributes to the inserted text.
"abc"at index-position 1 and make the insertion bold. Then we skip another character and insert
"xyz"without formatting attributes. E.g.
retaindelta may also contain formatting attributes that are applied on the retained text.
insertdelta is always an Array of inserted content in Y.Array & Y.XmlFragment.