Currently we only offer the picojson_traits that is also the default.

It would be ideal to provide all the known support traits

1. It's better for consumers
2. It's less duplication
3. easier to maintain

The proposal would be to have a header file for each support library

include/
├─ jwt-cpp/
│  ├─ jwt.h
│  ├─ base.h
│  ├─ traits/
│  │  ├─ picojson.h
│  │  ├─ nlohmann_json.h
│  │  ├─ jsoncons.h
│  │  ├─ boost_json.h

❓ Do we provide default specializations? This requires a define to make sure there's only one included
❓ Does this require a CMake option?
❓ What about badges for tested version?