[readme] add TWD module

README.md

@@ -162,7 +162,8 @@ allows booting application code via UART or from external SPI flash
 ([UART](https://stnolting.github.io/neorv32/#_primary_universal_asynchronous_receiver_and_transmitter_uart0),
 [SPI](https://stnolting.github.io/neorv32/#_serial_peripheral_interface_controller_spi) (SPI host),
 [SDI](https://stnolting.github.io/neorv32/#_serial_data_interface_controller_sdi) (SPI device),
-[TWI/I²C](https://stnolting.github.io/neorv32/#_two_wire_serial_interface_controller_twi),
+[TWI](https://stnolting.github.io/neorv32/#_two_wire_serial_interface_controller_twi) (I²C host),
+[TWD](https://stnolting.github.io/neorv32/#_two_wire_serial_device_controller_twd) (I²C device),
 [ONEWIRE/1-Wire](https://stnolting.github.io/neorv32/#_one_wire_serial_interface_controller_onewire))
 * general purpose IOs ([GPIO](https://stnolting.github.io/neorv32/#_general_purpose_input_and_output_port_gpio)) and
 [PWM](https://stnolting.github.io/neorv32/#_pulse_width_modulation_controller_pwm)