Returns the packaged country reference that maps an ISO3 code to the
standardised display name, polio risk tier and epidemiological zone groupings
the cleaners attach. Used by clean_afp() and clean_es() via
.polis_join_country().
Examples
head(polis_country_lookup())
#> # A tibble: 6 × 5
#> iso3 country_actual risk_group epi_zones epi_zones_v2
#> <chr> <chr> <chr> <chr> <chr>
#> 1 ABW NA NA Other Other
#> 2 AFG Afghanistan Endemic Other Other
#> 3 AGO Angola High Risk Central/Equatorial Africa Central/Equatorial …
#> 4 AIA NA NA Other Other
#> 5 ALA NA NA Other Other
#> 6 ALB Albania NA Other Other
