Add GTK4 dependency

Author: urbytes21

cmake/Dependencies.cmake

@@ -13,3 +13,13 @@ FetchContent_Declare(
 
 # Make GoogleTest available
 FetchContent_MakeAvailable(googletest)
+
+
+# ----------------------------------------------------------------------------------------
+# Dependencies - GTK4
+# ----------------------------------------------------------------------------------------
+# Use the package PkgConfig to detect GTK+ headers/library files
+find_package(PkgConfig REQUIRED)
+
+# Check for gtkmm-4.0 specifically, not just gtk4
+pkg_check_modules(GTKMM REQUIRED gtkmm-4.0)