Old version json.hpp

[nikita1prasolov]

Describe the issue
You have use old version of nlohmann/json - 3.5.0, feature request - switch to latest version 3.9.1

To Reproduce

• OS - all supported
• Compiler, compiler version, compile options - all supported
• Please attach minimal and reproducible .glTF file if you got an issue related to .glTF data - not applicable

Expected behaviour
Users can use improved and addition functionaliies

Screenshots

• not applicable

Additional context
Best regards, your user, Kit!

[syoyo]

You can use your own json.hpp with TINYGLTF_NO_INCLUDE_JSON ifdef: https://github.com/syoyo/tinygltf#compile-options

Currently there should be no issues using current json.hpp in TinyGLTF, so there isn't strong reason to update it.
We would only accept upgrading json.hpp if it gives faster C++ compilation time than the old version.

PR with benchmarks(C++ compile time) is welcome!

[nikita1prasolov]

Thank you!