Add cmake config file

Big thanks for @madebr who made all work

skeleton/imgui/CMakeLists.txt

@@ -0,0 +1,46 @@
+add_library(librw_skeleton_imgui
+    imconfig.h
+    imgui.cpp
+    imgui_demo.cpp
+    imgui_draw.cpp
+    imgui.h
+    imgui_impl_rw.cpp
+    imgui_impl_rw.h
+    imgui_internal.h
+    ImGuizmo.cpp
+    ImGuizmo.h
+    stb_rect_pack.h
+    stb_textedit.h
+    stb_truetype.h
+    )
+
+set_target_properties(librw_skeleton_imgui
+    PROPERTIES
+        PREFIX ""
+    )
+
+target_link_libraries(librw_skeleton_imgui
+    PUBLIC
+        librw_skeleton
+    )
+
+if(LIBRW_INSTALL)
+    install(
+        FILES
+            imconfig.h
+            imgui.h
+            imgui_impl_rw.h
+            imgui_internal.h
+            ImGuizmo.h
+            stb_textedit.h
+        DESTINATION "${LIBRW_INSTALL_INCLUDEDIR}/skeleton/imgui"
+        )
+
+    install(
+        TARGETS librw_skeleton_imgui
+        EXPORT librw-targets
+        RUNTIME DESTINATION "${CMAKE_INSTALL_BINDIR}"
+        LIBRARY DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+        ARCHIVE DESTINATION "${CMAKE_INSTALL_LIBDIR}"
+        )
+endif()