T - Add new attachment domains to CSP list

[limed]

For context see: https://github.com/mdn/infra/issues/354

Kuma now serves attachments from S3 via cloudfront, which means we will need to update the CSP list for stage and prod to include the attachment domains.

Acceptance Criteria

• [ ] The following domains will need to be added to CSP:

• https://media.stage.mdn.mozit.cloud

• https://media.prod.mdn.mozit.cloud

[tobinmori]

@callahad is this something you can add?