Add alt-right-click to delete reroutes (#899)

Alt-right-click to remove, regular right-click to show context menu.

src/LGraph.ts

@@ -1324,6 +1324,8 @@ export class LGraph implements LinkNetwork, Serialisable<SerialisableGraph> {
     }
 
     reroutes.delete(id)
+    // This does not belong here; it should be handled by the caller, or run by a remove-many API.
+    // https://github.com/Comfy-Org/litegraph.js/issues/898
     this.setDirtyCanvas(false, true)
   }