moveDown method
Moves this node down in parent's children.
Implementation
bool moveDown() {
if (!hasParent) return false;
var parentRuntime = this.parentRuntime;
var idx = indexInParent;
if (idx < 0) return false;
if (idx >= parentRuntime!.nodesLength - 1) return true;
remove();
var idxDown = parentRuntime._contentFromIndexForwardWhere(
idx, 1, (node) => domGenerator.isElementNode(node));
if (idxDown < 0) {
idxDown = parentRuntime.nodesLength;
}
parentRuntime.insertAt(idxDown, node);
return true;
}