Add highlight tests

tests/query/highlights/cpp/test.cpp

@@ -0,0 +1,17 @@
+#include <iostream>
+#include <cstdlib>
+//    ^ include
+//       ^ string
+
+auto main( int argc, char** argv ) -> int
+      //       ^ parameter
+      //    ^ type 
+      //    ^ TSType 
+      //                  ^ operator
+{
+    std::cout << "Hello world!" << std::endl;
+    
+    return EXIT_SUCCESS;
+    // ^ keyword.return
+    //      ^ constant
+}