Unsupported mimetype images load issue

[SlienceLambs]

Hi, I was doing some test using tinygltf. When loading images and mimeType is an unsupported type, the datauri will be used as the file name to find the file. here may be an issue if datauri size is too large.

[syoyo]

Can you post minimal, reproducible glTF file?

Anyway, parsing DaraURI in tinygltf is not perfect. We'll need to implement proper Data URI parser satisfying the Data URI Spec: https://tools.ietf.org/html/rfc2397