Split JSON implementation into its own library

.vscode/settings.json

@@ -154,5 +154,6 @@
     "modernize-*",
     "-modernize-use-nodiscard",
     "-modernize-use-trailing-return-type"
-  ]
+  ],
+  "python.pythonPath": "/usr/local/bin/python3"
 }

docs/index.md

@@ -40,7 +40,9 @@ See each header file for documentation.
   scattering, multiple importance sampling
 - [Yocto/ModelIO](yocto/yocto_modelio.md): parsing and writing for Ply/Obj/Pbrt
   formats
-- [Yocto/CommonIO](yocto/yocto_commonio.md): printing utilities, file io utilities,
+- [Yocto/CommonIO](yocto/yocto_commonio.md): JSON data type, json io utilities,
+  command line parsing
+- [Yocto/JSON](yocto/yocto_json.md): printing utilities, file io utilities,
   command line parsing
 - [Yocto/Common](yocto/yocto_common.md): container and iterator utilities
 - [Yocto/Parallel](yocto/yocto_parallel.md): concurrency utilities

docs/yocto/yocto_json.md

@@ -0,0 +1,12 @@
+# Yocto/JSON: Utilities for manipulating JSON data
+
+Yocto/JSON is an implementation of a utilities for hanlding JSON data,
+including a Json variant data type, loading, saving and formatting JSON,
+and a parser for command line arguments to JSON.
+Compared to other libraries, it is more lightweight and provides a common
+implementation for the rest of Yocto/GL.
+Yocto/JSON is implemented in `yocto_json.h` and `yocto_json.cpp`, and
+depends on `json.hpp`.
+
+**This library is experimental** and will be documented appropriately when
+the code reaches stability.

libs/yocto/CMakeLists.txt

@@ -10,6 +10,7 @@ add_library(yocto
   yocto_trace.h yocto_trace.cpp
   yocto_sceneio.h yocto_sceneio.cpp
   yocto_commonio.h yocto_commonio.cpp
+  yocto_json.h yocto_json.cpp
   ext/stb_image.h ext/stb_image_resize.h ext/stb_image_write.h ext/stb_image.cpp
   ext/cgltf.h ext/cgltf_write.h ext/cgltf.cpp
   ext/json.hpp