add scripts for 12 month enrollment

[AlisonLanski]

• [x] Write part A
• [x] Write part B
• [x] Write part C
• [x] Write wrapper function
• [x] Create google sheet for import specs
• [x] Create RMD vignette that reads in google sheet
• [x] Create dummy data
• [x] Test functions using dummy data
• [x] Test functions using real data
• [x] Save dummy data as a .rda to the package
• [x] Save google sheet as .dat to the package
• [x] Run devtools::check() and address errors

[AlisonLanski]

@shilohfling I think this is done now but I would appreciate a once-over for documentation or running things using dummy data etc.

[shilohfling]

Validated baybeeee!!!