libobs: Log when libobs data file is not found

When an effect file is not found while initializing graphics, only one
line error below is logged. To clarify the reason why the initialization
was failed, also log when the file was not found.
Failed to initialize video. Your GPU may not be supported, or your
graphics drivers may need to be updated.

libobs/obs.c

@@ -1284,6 +1284,9 @@ char *obs_find_data_file(const char *file)
 			return path.array;
 	}
 
+	blog(LOG_ERROR, "Failed to find file '%s' in libobs data directory",
+	     file);
+
 	dstr_free(&path);
 	return NULL;
 }