Add CMake build and client support

example/CMakeLists.txt

@@ -0,0 +1,34 @@
+cmake_minimum_required(VERSION 3.15)
+
+project(async-mqtt5-examples CXX)
+
+include(../cmake/project-is-top-level.cmake)
+
+if(PROJECT_IS_TOP_LEVEL)
+  find_package(async_mqtt5 REQUIRED)
+endif()
+
+function(add_example name)
+  add_executable("${name}" ${ARGN})
+  target_compile_features("${name}" PRIVATE cxx_std_20)
+  target_link_libraries("${name}" PRIVATE Async::MQTT5)
+endfunction()
+
+foreach(f callbacks cpp20_coroutines futures publisher receiver)
+  add_example("${f}" "${f}.cpp")
+endforeach()
+
+#[[
+add_example(
+    misc
+    src/run_examples.cpp
+    network_connection.cpp
+    openssl-tls.cpp
+    tcp.cpp
+    websocket-tcp.cpp
+    websocket-tls.cpp
+)
+
+find_package(OpenSSL REQUIRED)
+target_link_libraries(misc PRIVATE OpenSSL::SSL)
+]]