Register MIME Type for GLB File Format

[lexaknyazev]

Since GLB file format is now a part of glTF 2.0 core spec, we should register its MIME Type with IANA.

According to RFC 6838, Section 4.2, we can use neither . (dot) because gltf is facet-less tree, nor + (plus) because it means registered structured syntax suffix (such as +json or +xml). So we've got two options (at least):

• model/gltf-binary
• model/gltf_binary

Thoughts?

CC @pjcozzi @sbtron @bghgary

[pjcozzi]

Replaces #650

CC #412

[pjcozzi]

model/gltf-binary

+1

[emackey]

+1 for model/gltf-binary

We'll have to fix it in Cesium, which is currently using model/gltf.binary.

[sbtron]

Updated in #1000 . Still need to register with IANA

[sbtron]

gltf-binary is now registered with IANA-
https://www.iana.org/assignments/media-types/media-types.xhtml

[pjcozzi]

Really exciting, congrats and thanks for taking the lead on this!