Tutorial typo fix (due to renaming?)
I think this fixes a small typo in the "responding to events" tutorial (crosshairs must have been renamed to markers earlier, because at that point in the tutorial, no object with this name has been introduced).
"```python\n",
"X = Stream.define('X',x=0.0)\n",
"Y = Stream.define('Y',y=0.0)\n",
- "hv.DynamicMap(crosshairs, streams=[X(),Y()])\n",
+ "hv.DynamicMap(marker, streams=[X(),Y()])\n",
"```\n",
"\n",
"The reason why you might want to list multiple streams instead of always defining a single stream containing all the required stream parameters will be made clear in the [Custom Interactivity](./12-Custom_Interactivity.ipynb) guide."
