Graphs for Final Font Size

Here's my attempt at creating a graph that has the total bytes transferred
for a font across the three tested methods:

https://github.com/w3c/PFE-analysis/pull/56/files

Some notes:

   - I stuck with the same style graph as used in the percentage graphs as
   it lets us easily show distributions. I changed the line colour to blue
   since there's no good/bad distinction on this graph.
   - I derived the values on the graph by applying the percentage
   reductions from the simulation results to the "worst case" woff2 font size
   for each language group (the 95th percentile font size).
   - This gives an estimate of the amount of bytes that would be
   transferred for a font of that size.
   - However, there are a couple important caveats:
      - % reduction from the simulation is the reduction over a sequence of
      page views and is *not representative of the reduction in bytes
      transferred for loading a single page*. The reduction for a single
      page is likely to be higher than for a sequence of page views.
      - Similarly the reduction is the aggregate of all fonts on a given
      page. So for something like CJK that means there could be latin or other
      language fonts mixed in. Thus the percent reductions *are not
      representative of the reductions you'd see for a single CJK font in
      isolation*. Again I believe the reduction is actually larger for a
      single CJK font on a single page.
   - Unfortunately the simulation results were not recorded at the font
   level but at the page view level, so there isn't a way to the true per font
   reduction percentages out of the results we currently have.


Next up I'm working on generating graphs of the font size distributions.