Add text for "Use existing Data"

[avahoffman]

Filling out the text for the "Bring existing data" section. This includes:

1. Where can you find data?
   • https://anvilproject.org/data
   • https://anvil.terra.bio/#library/datasets
   • Data dashboard
   • Gen 3
   • Data library/feat workspaces

Remember to remind users about how links are copied to data tables when cloning a workspace