Add per-benchmark over-time plot to comparisons

[smarr]

It would be nice to have a new icon in the comparison view, which when clicked, would render a time-line plot, i.e., the historic values over time.

I think, based on the commit ids, we hopefully can determine the baseline branch, and the branch of the change, and show the last up-to N (perhaps 100 or so) measurements.

Thoughts:

• uPlot seems a better candidate, for scalability than plotly https://github.com/leeoniya/uPlot
• relevant demos for showing the high/low range: https://leeoniya.github.io/uPlot/demos/high-low-bands.html
• possible icons
  • https://icons.getbootstrap.com/icons/graph-up/
  • https://icons.getbootstrap.com/icons/activity/
  • https://icons.getbootstrap.com/icons/clipboard-pulse/
  • https://icons.getbootstrap.com/icons/clock-history/
  • https://icons.getbootstrap.com/icons/rewind-circle/
  • https://icons.getbootstrap.com/icons/rewind/

Status Update

PR #106 implements the first version of this.
There are features that would still be good to add at a later point:

• limit the requested data to 100 points (per branch?)
• make data points clickable, e.g., based on https://leeoniya.github.io/uPlot/demos/tooltips-closest.html