* Move UDLs into nlohmann::literals::json_literals namespace
* Add 'using namespace' to unit tests
* Add 'using namespace' to examples
* Add 'using namespace' to README
* Move UDL mkdocs pages out of basic_json/
* Update documentation
* Update docset index
* Add JSON_GlobalUDLs CMake option
* Add unit test
* Build examples without global UDLs
* Add CI target
* Fix patch::add creating nonexistent parents
The previous behavior was not in accordance with RFC6902.
Add unit test.
Fixes#3134.
* Fix incorrect JSON patch unit test
Co-authored-by: Hudson00 <yagdhscdasg@gmail.com>