CMake: Add fileoverlay icons for cmake project files

Change-Id: Id9b8aa9b1902e6f88ca4e8bde2e5f20281a77437
Reviewed-by: Tobias Hunger <tobias.hunger@qt.io>
Reviewed-by: Alessandro Portale <alessandro.portale@qt.io>

src/plugins/cmakeprojectmanager/cmakeprojectconstants.h

@@ -54,5 +54,8 @@ const char CMAKE_SETTINGSPAGE_ID[] = "Z.CMake";
 // Snippets
 const char CMAKE_SNIPPETS_GROUP_ID[] = "CMake";
 
+// Icons
+const char FILEOVERLAY_CMAKE[] = ":/cmakeproject/images/fileoverlay_cmake.png";
+
 } // namespace Constants
 } // namespace CMakeProjectManager