add an async subscriber impl with thread pool

subscriber-notifs-async/CMakeLists.txt

@@ -0,0 +1,15 @@
+cmake_minimum_required(VERSION 4.0)
+
+project(subscriber-notifs VERSION 1.0)
+set(CMAKE_CXX_STANDARD 20)
+
+file(GLOB_RECURSE SRC_FILES "src/*.cpp")
+file(GLOB_RECURSE HEADER_FILES "include/*.hpp")
+
+add_executable(sub_notifs ${SRC_FILES} ${HEADER_FILES})
+
+target_include_directories(sub_notifs PRIVATE include )
+
+# from: https://cmake.org/cmake/help/latest/module/FindThreads.html
+find_package(Threads REQUIRED)
+target_link_libraries(sub_notifs PRIVATE Threads::Threads)