Uploads multiple evidence files for a chargeback in a single request. Each part of the multipart body must be keyed by an evidence type (see the evidence-types endpoint for the valid values for this chargeback), with exactly one file per evidence type. Limits: at most 10 files per request, at most 2MB per file, and only application/pdf, image/jpeg or image/png content is accepted. The chargeback must be in the action_required status, and none of the submitted evidence types may already exist on the chargeback. On success the chargeback transitions to pending_review.