List the topic subcategories, which can be
used to filter topics within ha_topics().
Examples
# \donttest{
ha_set("chicagohealthatlas.org")
ha_subcategories()
#> # A tibble: 30 × 3
#> subcategory_name subcategory_key category_name
#> <chr> <chr> <chr>
#> 1 Access to Care access-to-care Clinical Care
#> 2 Quality of Care quality-of-care Clinical Care
#> 3 Community Safety community-safety-1 Physical Environment
#> 4 Housing & Transit housing-transit Physical Environment
#> 5 Pollution pollution Physical Environment
#> 6 Resource Availability resource-availability Physical Environment
#> 7 Behavioral Health behavioral-health Morbidity
#> 8 Chronic Disease chronic-disease-1 Morbidity
#> 9 Infectious Disease infectious-disease-1 Morbidity
#> 10 Injury & Violence injury-violence-1 Morbidity
#> # ℹ 20 more rows
# }