Added JSON support. (0.28.0)

docs/handbook.md

@@ -46,7 +46,8 @@ cd fun
 Build:
 
 ```bash
-cmake -S . -B build -DFUN_DEBUG=OFF -DFUN_WITH_PCSC=OFF -DFUN_WITH_REPL=ON
+# Note: Every -D flag must be of the form NAME=VALUE (e.g., -DFUN_WITH_REPL=ON)
+cmake -S . -B build -DFUN_DEBUG=OFF -DFUN_WITH_PCSC=OFF -DFUN_WITH_REPL=ON -DFUN_WITH_JSON=ON
 cmake --build build --target fun
 ```
 
@@ -79,6 +80,22 @@ FUN_LIB_DIR="$(pwd)/lib" ./build/fun
 
 But be sure to build Fun with -DFUN_WITH_REPL=ON.
 
+#### CMake options
+
+All CMake options must be passed as -DNAME=VALUE:
+
+- FUN_DEBUG=ON|OFF — verbose debug logging in the VM (default OFF)
+- FUN_WITH_REPL=ON|OFF — enable the interactive REPL (default ON)
+- FUN_WITH_PCSC=ON|OFF — enable PC/SC smart card support (default OFF)
+- FUN_WITH_JSON=ON|OFF — enable JSON support via json-c (default OFF)
+
+If you encounter an error such as:
+
+  CMake Error: Parse error in command line argument: FUN_WITH_JSON
+  Should be: VAR:type=value
+
+then a -D option was given without a value. Always use -DNAME=VALUE, for example -DFUN_WITH_JSON=ON.
+
 ### Install Fun to OS
 
 I do not recommend installing Fun on your system because it is in a very early