This work improves the accessibility of the add and change pages in the
admin site by adding <details> and <summary> elements to the collapsible
fieldsets. This has the nice side effect of no longer requiring custom
JavaScript helpers to implement the fieldsets' show/hide capabilities.
Thanks to James Scholes for the accessibility advice, and to Sarah Boyce
and Tom Carrick for reviews.
Co-authored-by: Natalia <124304+nessita@users.noreply.github.com>
Co-authored-by: Sarah Boyce <42296566+sarahboyce@users.noreply.github.com>