Add TxDOT Traffic Data

[johnhryhorchuk]

While the Google mobility and SafeGraph data is more important, we also have the option of linking into the data that powers DriveTexas.org. While I'm not immediately aware of what we would learn from this source vs. Google/SafeGraph, it is worth pursuing (a) to establish a relationship that will be longer-lasting and (b) they might collect data points we don't even know about yet. I could imagine them having data that helps project motor fuels tax revenues.