Support Rotary Encoders on an IO Expander

**Describe the problem you have/What new integration you would like**

I want to use a rotary Encoder connected to a PCF8574. Currently it's only supported that the pins from the encoder are directly connected.

**Please describe your use case for this integration and alternatives you've tried:**

I have a custom PCB layout where I don't have enough pins available on the ESP. Therefore the rotary encoder needs to be connected to a PCF8574

**Additional context**

[https://github.com/RobTillaart/rotaryDecoderSwitch/issues/4]
Seems like there is a component available which can help. Maybe this can be used as an external component or someone can point me in the direction how I can use this component and convert it to a external component (complete newby here. Never done anything like that before).

Thanks a lot.

Start by reviewing how ESPHome currently supports rotary encoders and how PCF8574 pins are exposed to components. Compare the requested behavior with the linked rotaryDecoderSwitch component and determine whether it can be used as an external component. Done means a rotary encoder connected through a PCF8574 works in ESPHome.

Written by the indexing model from the issue text.