[metrics-team] Demo: relay, bridge, and PT graphs all on one page

[David Fifield]

Please see:
https://people.torproject.org/~dcf/metrics-country.html

Whenever I look at one of these metrics graphs, I almost always want to
look at the other two:
https://metrics.torproject.org/userstats-relay-country.html
https://metrics.torproject.org/userstats-bridge-country.html
https://metrics.torproject.org/userstats-bridge-combined.html
But it's cumbersome to always manage three tabs and keep the date ranges
synced between them. So I made the above page that puts them all
together.

It uses JavaScript but you could in principle do the same thing with
server-side code. It handles query parameters like the metrics graphs
do, for example:
https://people.torproject.org/~dcf/metrics-country.html?country=tr
https://people.torproject.org/~dcf/metrics-country.html?start=2012-01-01
https://people.torproject.org/~dcf/metrics-country.html?start=2016-06-01&end=2017-05-01&country=br

It would be better if the space allocated for the vertical axis labels
were consistent. As it is, if the relay graph goes up to 10,000 and the
bridge graph goes up to 800, the horizontal tick marks won't exactly
line up because of different amounts of space allocated on the left.