Patch release FBX2glTF v0.9.7

This is a small but important bugfix patch to release 0.9.6:

• Fixed a struct initialisation issue which could damage vertex deduplication in the presence of blend shapes, leading to redundant, bloated output files. In practice, the problem seems to have been constrained to Windows, but we recommend everyone upgrade.

A few more goodies:

• @shrinktofit added --fbx-tmp-dir to control over where the FBX SDK writes temporary files: #219
  • (By default the SDK will e.g. create a MyAsset.fbm folder next to your MyAsset.fbx file. This was always poor form; the location of a source asset should be considered read-only.)
• @FreakTheMighty added code to properly infer output folder in the common case when -o/--output refers to a .gltf file: #193
• We now use the correct field-of-view properties on FbxCamera in all cases. Fixes #209.
• Fixed the $OSTYPE script snippet in README.md. Fixes #214.