New plot: station additions over time

[ryan-williams]

It would be cool to visualize the expansion of the system geographically over time, from Manhattan out to the other boroughs, Jersey City, and Hoboken.

[ryan-williams]

WIP: db26b87..colors

Yellow = earliest stations (beginning June 2013)
Red = most recently added stations (through Feb 2023)

Tweeted at https://twitter.com/EmMorgen/status/1633633353311088652

Also in the repo here, live at https://ctbk.dev/img/stations-by-creation-date.png