Add target.object to capture.props in exemplary pipewire config

[jkhsjdhjs]

The readme currently gives an exemplary pipewire config using the filter-chain module, which really helps when setting this up. The filter chain simply listens on the default source, which might not be the source you actually want it to use. To get around this, you can specify a target source as input for the filter-chain (thanks to @licentiapoetica for figuring this out):

capture.props = {
    node.name =  "capture.rnnoise_source"
    node.passive = true
    audio.rate = 48000
    target.object = "alsa_input.usb-Logitech_Logitech_G930_Headset-00.mono-fallback"
}

I propose to either add this to the example or at least note it somewhere, so that other users don't face the same issue as I did.

See also: https://github.com/werman/noise-suppression-for-voice/issues/162#issuecomment-1677979108