Make width of charts with and without y2 axis line up

[ben-spiller]

Is your feature request related to a problem? Please describe the use case.
Many of the charts in overview.html have a 2nd (y2) axis, which takes up some space on the right of the chart... but others don't, and the different widths of the plot area make it hard to compare the same time across charts.

Describe the solution you'd like
The width of charts without a y2 axis should be reduced to match the width of the charts that do have it. BUT this needs to happen without breaking the automatic horizontal resizing to width.

We use the https://dygraphs.com/options.html# library for generating the charts. If someone could figure out how to do it in the HTML (perhaps in the attached sample file overview.html.txt ), adding it to the .py would be easy. Any HTML/JS/CSS experts out there want to have a go?