Add "Excess Mortality" Data

[johnhryhorchuk]

Stakeholders have requested that we track excess mortality that has occurred during this COVID period. CDC data for Texas is readily available: https://www.cdc.gov/nchs/nvss/vsrr/covid19/excess_deaths.htm

In playing with the CDC data, my initial reaction is that we appear to be having a greater number of excess deaths caused by non-COVID issues.