add CH422 support

[omelia-iliffe]

Hi!

I've been working recently with a Waveshare ESP32-S3-Touch-LCD-7 which uses a CH422 IO chip (datasheet) for some of its core functions.
So I've had a go at adding support for it to the crate.

It's a bit a strange chip:

• it has 12 pins:
  • a set of 4 output pins with 2 modes (push pull or open drain)
  • a set of 8 with 2 modes (inputs or push pull outputs)
• the modes of the two sets control the entire set
• no i2c address so the commands have to be bit shifted before being sent as an address

my work in progress implementation just supports the 8 io pins. It uses type state for switch between the two modes (input and output) but I'm not sure this is the right solution for a couple of reasons.

• When created the library assumes it will be in input mode, it may not be
• When changing modes the user has to specify the PortMutex generic, let mut io: port_expander::Ch422<RefCell<_>> = port_expander::Ch422::new(i2c).enable_output().unwrap();
• the enable_output method is fallible and will drop the Port if it returns an Err

But using typestate means that when we call split, the Pins have the correct mode.