Mermaid chart should report the rows, columns and time of the resultset

Currently, the mermaid version of the query plan doesn't display information about the result of the query, this could be done by adding a "HEAD" node:

~~~
NODE_HEAD@{ shape: sm-circ }
~~~

and an edge to this node, something like this:

~~~
NODE_xxxxxxxxxx -- 0 rows<br />0 columns<br />0 bytes<br />0ms --> NODE_HEAD
~~~