Create an install target for the project

CMakeLists.txt

 cmake_minimum_required(VERSION 3.0)
 
-project(json CXX)
+# define the project
+project(json VERSION 2.0.0 LANGUAGES CXX)
 
+# define project variables
 set(JSON_TARGET_NAME ${PROJECT_NAME})
 set(JSON_UNITTEST_TARGET_NAME "json_unit")
 set(JSON_PACKAGE_NAME ${JSON_TARGET_NAME})
 set(JSON_TARGETS_FILENAME "${JSON_PACKAGE_NAME}Targets.cmake")
+set(JSON_CONFIG_FILENAME "${JSON_PACKAGE_NAME}Config.cmake")
+set(JSON_CONFIGVERSION_FILENAME "${JSON_PACKAGE_NAME}ConfigVersion.cmake")
+set(JSON_CONFIG_DESTINATION "cmake")
+set(JSON_INCLUDE_DESTINATION "include/nlohmann")
 
+# create and configure the library target
 add_library(${JSON_TARGET_NAME} INTERFACE)
 target_include_directories(${JSON_TARGET_NAME} INTERFACE
-  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/src>)
+  $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/src>
+  $<INSTALL_INTERFACE:${JSON_INCLUDE_DESTINATION}>)
 
+# create and configure the unit test target
 add_executable(${JSON_UNITTEST_TARGET_NAME}
     "test/catch.hpp" "test/unit.cpp")
 set_target_properties(${JSON_UNITTEST_TARGET_NAME} PROPERTIES
@@ -21,6 +30,28 @@ set_target_properties(${JSON_UNITTEST_TARGET_NAME} PROPERTIES
 target_include_directories(${JSON_UNITTEST_TARGET_NAME} PRIVATE "test")
 target_link_libraries(${JSON_UNITTEST_TARGET_NAME} ${JSON_TARGET_NAME})
 
+# generate a config and config version file for the package
+include(CMakePackageConfigHelpers)
+configure_package_config_file("cmake/config.cmake.in"
+    "${CMAKE_BINARY_DIR}/${JSON_CONFIG_FILENAME}"
+    INSTALL_DESTINATION ${JSON_CONFIG_DESTINATION})
+write_basic_package_version_file("${CMAKE_BINARY_DIR}/${JSON_CONFIGVERSION_FILENAME}"
+    VERSION ${PROJECT_VERSION}
+    COMPATIBILITY SameMajorVersion)
+
+# export the library target and store build directory in package registry
 export(TARGETS ${JSON_TARGET_NAME}
 	FILE "${CMAKE_BINARY_DIR}/${JSON_TARGETS_FILENAME}")
 export(PACKAGE ${JSON_PACKAGE_NAME})
+
+# install library target and config files
+install(TARGETS ${JSON_TARGET_NAME}
+	EXPORT ${JSON_PACKAGE_NAME})
+install(FILES "src/json.hpp"
+	DESTINATION ${JSON_INCLUDE_DESTINATION})
+install(EXPORT ${JSON_PACKAGE_NAME}
+	FILE ${JSON_TARGETS_FILENAME}
+	DESTINATION ${JSON_CONFIG_DESTINATION})
+install(FILES "${CMAKE_BINARY_DIR}/${JSON_CONFIG_FILENAME}"
+	"${CMAKE_BINARY_DIR}/${JSON_CONFIGVERSION_FILENAME}"
+	DESTINATION ${JSON_CONFIG_DESTINATION})

cmake/config.cmake.in

+@PACKAGE_INIT@
+
+cmake_policy(PUSH)
+cmake_policy(SET CMP0024 OLD)
+include(${CMAKE_CURRENT_LIST_DIR}/@JSON_TARGETS_FILENAME@)
+cmake_policy(POP)
\ No newline at end of file