Add 'Description' label

[Kistine]

• [x] programmatically update all of the Description fields for all four dimensions at once to start with 'Description:' rather than going in and pasting into each one

[laurenancona]

closed in https://github.com/CityOfPhiladelphia/community-health-explorer/commit/954c48113ecb388042924d75867b72a9ba1d845a