added a comment in textstream.h

src/textstream/textstream.h

@@ -86,6 +86,9 @@ public:
 	const_iterator begin() const;
 	const_iterator end() const;
 
+	// IMPROVE ME
+	// add cbegin(), cend(), rbegin(), rend(), crbegin(), crend()
+
 	void to_string(std::string & str,  bool clear_string = true) const;
 	void to_string(std::wstring & str, bool clear_string = true) const;