sociome 3.0.0

Large overhaul:

• 2020 decennial census is now completely supported.
• Removed seed argument from get_adi(), calculate_adi(), and synthetic_population().
• Added the helper objects state_geoids (a character vector of the state geoids for which ADI values can be created) and dataset_year_geography_availability, which outlines the combinations of dataset, year, and geography are available from the census API as well as which combinations can be used to obtain ADI values.
• Better input checking so that sociome will inform the user proactively if they won't be able to obtained what they requested from the census API.
• Expanded ZCTA availability and fixed ZCTA-related bugs.
• Added lots of unit tests.