Convert a two-letter location abbreviation to a two-character FluSight location code
Source:R/forecasttools.R
loc_abbr_to_flusight_code.Rd
Given a vector of state/territory two-letter
USPS short names (e.g. MA, TX, PR), return
the corresponding FluSight challenge location
code (legacy FIPS code for states and territories,
US
for the US).