Events collection: Add media file upload list & update UI to accommodate multiple files

[LibbyUX]

Summary

Users need the capability to add multiple files/links to event entries:

• Posters: PNG, PDF, JPEG
  • This is generally promotional event images, such as flyers, that contain details about the event
• Slides: PDF
• Photos: Link to Google Drive, Google Photos, or other photo sharing platform
• Website: Link to relevant website or PDF of website

This is especially relevant for #107 and needed in order to complete this manual data entry as Amatria related events tend to have more media.

Documentation

@axdanbol and I looked into this and we can achieve this via Decap's list widget.

• https://decapcms.org/docs/widgets/#List

Design todo

• config: Specify fields, labels, and hint text
• cns.iu.edu/research | List view: Redesign public-facing list item component
• cns.iu.edu/research | Gallery view: Redesign gallery view - Swap gallery card for collection card
• Handoff to dev

Dev todo

• Implement component updates to list item in list view
• Implement component updates to gallery view