Breaks this node into two nodes at the specified offset
( int $offset
After being split, this node will contain all the content up to the
offset. If the original node had a parent node,
the new node is inserted as the next sibling of the original node.
When the offset is equal to the length of this node,
the new node has no data.
The offset at which to split, starting from 0.
The new node of the same type, which contains all the content at and after the