I2S on generic pico 2040

[davidegironi]

Hello Marcel,
I've compile and upload your project on a Generic pi2040.
I'm listening through pwm audio using the schematic found in the following page https://github.com/rgrosset/pico-pwm-audio
The audio quality is not that good up to me, so I would like to try a I2S board.
Commenting out the RP2040_AUDIO_PWM macro set the I2S mode. The problem is that the compiler tells me I2S library is not defined. Did I miss something? I'using Arduino 2 IDE.
By the way thank you for your effort on this project.