Update Vignette due to datanames updates

[donyunardi]

Summary

Related to #333, let's update our vignette to fully explain this new feature.

Acceptance Criteria

The following topics must be covered:

• The use of a dot prefix in object names within a teal_data object
• What happens if you don't use a dot prefix
• Behavior when a function is included in teal_data
• How module(datanames) relates to names(teal_data)
• What happens when using module(datanames = "all") vs module(datanames = "<specific data object>")
• What happens when using transform(datanames = "all") vs transform(datanames = "<specific data object>")
• Discussion on set_datanames
• Listing all possible scenarios between module(datanames) and transform(datanames)
  Can use this table as an example: datanames slot in teal_transform_module (ignore @datanames) teal#1334 (comment)