Add heuristic for fixing semantically disconnected edges/labels in draw.io diagrams

If the author of a draw.io diagram added a text field on top of an edge without actually connecting it to the edge, this tool will parse it as an isolated node rather than an edge label. Similarly, an unconnected edge will semantically not be connected to its source/destination even if looks visually aligned in the draw.io editor.

To fix these issues, it would be nice if we could have an (optional?) heuristic that tries to "fix" the diagram's semantic structure by assigning labels or arrows to the (visually) nearest node or edge.