Request for RR extension prefix

**Requested Prefix:** RR
**Company or Project Name:** Remixing Reality
**Vendor Contact Information:** tom@remixingreality.com

No file, test, or entry point is named. Start by locating how glTF extension prefixes are recorded and review comparable prefix requests; the work is done when the RR prefix, Remixing Reality name, and supplied vendor contact are recorded in the appropriate project location.

Written by the indexing model from the issue text.