Allow splitting data across two spreadsheets: roster and check-ins

Would be great if one spreadsheet was a list of people with details -- the "roster" csv. The table should work with just that. It's easy to maintain manually, and can easily be generated or updated via script from meetup or slack or other platforms (which will be done perhaps via `civictechto/civictechto-scripts`).

roster sample: https://docs.google.com/spreadsheets/d/1LCVxEXuv70R-NozOwhNxZFtTZUmn1FLMPVD5wgIor9o/edit#gid=642523045
check-in sample: https://docs.google.com/spreadsheets/d/1LCVxEXuv70R-NozOwhNxZFtTZUmn1FLMPVD5wgIor9o/edit#gid=1061878392

But it would also be nice to have another CSV for status check-ins. It would be somehow appended rows to this sheet either based on feedback or forms or interactive slack messages or whatever. New rows could be added with just an update of the "status" (eg. active, inactive, or whatever works). The row would also need an identifier to join with the roster table -- perhaps a slack or meetup id.

So then we could provide this embedded iframe not just the roster csv, but another from which if could render features to show who's active or not -- perhaps adding another column, or maybe adding a little form input to scroll through time and see active organizers over time, or maybe filtering based on status. How it's displayed is up for discussion, but having that data split out would be helpful regardless :)

No files, tests, or entry points are named. Start by reviewing the experimental app described in the repository and the linked roster and check-in spreadsheet samples; clarify the data join, status history, and desired embedded display before implementation can be considered done.

Written by the indexing model from the issue text.