add syntax checking with issue highlighting

src/main.cpp

@@ -9,6 +9,13 @@ int main(int argc, char **argv)
 	}
 
 	std::vector<Expression::Token> tv = Parser::tokenize_input(argv[1]);
+
+	if (Syntax::check_syntax(tv))
+	{
+		return 0;
+	}
+
 	Syntax::apply_corrections(tv);
+
 	std::vector<Expression::Operation> ov = Syntax::build_op_vector(tv);
 }