Extension:3D/bg

The 3d extension gives the user of a wiki support for uploading and viewing 3d models.

It currently supports the AMF and STL file formats from the 3d printing world.

Short-term plan for Wikimedia production release

 * 1) ✅ Upload and hooks for 2D rendering code made into this extension
 * 2) ✅ Code review for T132064 (282211) - "Make Media Viewer pluggable for the 3d extension, videos, …"
 * 3) Deploy to Beta Cluster for testing, bug-discovery, and further editor feedback
 * 4) Request UI/UX input on possible fixes & improvements, in the short-term and medium-term

Related tasks
Deployment of this tool: T132058 - 3d extension supporting AMF and STL (3d printing files) Other 3D file support:
 * T54655 - Add support for thumbnails and interactive views of 3D models
 * T132064 - Make Media Viewer pluggable for the 3d extension, videos, …
 * T132063 - Security review of 3d2png
 * T3790 - Allow uploading of 3D files to Wikimedia Commons
 * T131723 - Provide a mechanism to sanitise user-generated 3D files to meet security requirements