Avoids misuse of selectPrevious/Next as per prior commit which was then
causing problems elsewhere, and is probably best to avoid creation in
those select methods anyway.
Updated up/down handling to create where a selection candidate does not
exist, to apply to a wider scenario via the selectPrevious/Next methods.
Updated DOM selection change handling to identify single selections
within decorated nodes to select them in full, instead of losing
selection due to partial selection of their contents.
Updated table selection handling so that our colgroups are ignored for
internal selection focus handling.
Added list nesting support to allow li > ul style nesting which lexical
didn't do by default.
Adds tab handling for inset/outset controls.
Will be a range of edge-case bugs to squash during testing.
Dan Brown