Enable range selection of checkboxes

[RuthShryock]

Checklist

1. If you've added code that should be tested, add tests
2. If you've changed APIs, update (or create!) the documentation
3. Ensure the tests pass
4. Make sure that your code lints and that you've followed our coding style
5. Write a title and, if necessary, a description of your work suitable for publishing in our release notes
6. Mention any related issues in this repository (as #ISSUE) and in other repositories (as kobotoolbox/other#ISSUE)
7. Open an issue in the docs if there are UI/UX changes

Notes

Modified the bulkUpdateChange function to handle range selection by updating the state of selected checkboxes between the initial and final checkbox selection while the Shift key is pressed.

Related issues

Fixes #3995

[notion-workspace]

Enable selecting range of checkboxes

[LMNTL]

This works pretty well! The only change I would request is fairly small: it might be better if selecting the range only happened if you held the shift key down while selecting the start and end checkboxes (instead of just the end checkbox.)