Code related to possible options has been pruned. It was pointless for
updateNode to take a node as input. Collapsing documentation items does
not make sense given the greater space of a sidebar tab compared to a
floating window on the graph, so the corresponding code has been fully
pruned as well.
The topmost node is used instead of the current_node. While current_node
displayed the desired properties when canvas was still shallowReactive
of notifying a change in node, it's not intended to be used external to
litegraph and at best, tracks the topmost visible node instead of the
actual topmost node.
A test expectation screenshot has been added for verifying theming works
for the documentation tab.
