Get the URL for PL files for a particular state and year
pl_url(abbr, year = 2010)
a character vector containing the URL to a ZIP containing the PL files.
pl_url("RI", 2010)
#> [1] "https://www2.census.gov/census_2010/01-Redistricting_File--PL_94-171/Rhode_Island/ri2010.pl.zip"