Add virtual converter output interface

typefactory/convertlatex.h

@@ -0,0 +1,13 @@
+#ifndef CONVERTLATEX_H
+#define CONVERTLATEX_H
+
+#include "converter.h"
+
+class ConvertLatex final : public Converter {
+public:
+  using Converter::Converter;
+
+  bool save (const std::string &output_file_name) override;
+};
+
+#endif // CONVERTLATEX_H