update unit tests

tests/core_test.cpp

 #include "../src/lib/core.hpp"
 
 #include <gtest/gtest.h>
-#include <filesystem>
 
+#include <filesystem>
 #include <opencv2/core/core.hpp>
 
 using namespace videoanalyser;

tests/files_test.cpp

 #include "../src/lib/files.hpp"
+
 #include <gtest/gtest.h>
 
 using namespace files;