Add sigslot library

Author: adazem009

CMakeLists.txt

@@ -79,8 +79,18 @@ include_directories(thirdparty/spimpl)
 FetchContent_Declare(json URL https://github.com/nlohmann/json/releases/download/v3.11.3/json.tar.xz)
 FetchContent_MakeAvailable(json)
 
+set(SIGSLOT_COMPILE_TESTS OFF)
+set(SIGSLOT_COMPILE_EXAMPLES OFF)
+FetchContent_Declare(
+  sigslot
+  GIT_REPOSITORY https://github.com/palacaze/sigslot
+  GIT_TAG        19a6f0f5ea11fc121fe67f81fd5e491f2d7a4637 # v1.2.0
+)
+FetchContent_MakeAvailable(sigslot)
+
 target_link_libraries(scratchcpp PRIVATE nlohmann_json::nlohmann_json)
 target_link_libraries(scratchcpp PRIVATE zip)
+target_link_libraries(scratchcpp PUBLIC Pal::Sigslot)
 target_link_libraries(scratchcpp PRIVATE scratchcpp-audio)
 
 if (LIBSCRATCHCPP_NETWORK_SUPPORT)