Make node clickable

According to [request here](https://www.reddit.com/r/dataisbeautiful/comments/9yg8w9/googles_autocomplete_visualized_like_a_graph_link/ea1lroo) when clicking on a node we want to start a new search from this node.

I'm not sure how this trigger should work yet - whether a single click should do it, or maybe double? Or maybe single click should just show a context menu with possible actions (start search, open it on google, etc.).

Start by resolving the interaction design left open in the issue: single click, double click, or a context menu with actions. Then locate the visualization's node interaction entry point; done means an agreed node action starts a new search, with any additional agreed actions behaving consistently.

Written by the indexing model from the issue text.