Suggestion: Clarify how multiple data pins work in `keypad.ShiftRegisterKeys`

[aseanwatson]

I was looking into using keypad.ShiftRegisterKeys and found the documentation confusing. I had to check the source code to understand how it works.

https://github.com/adafruit/circuitpython/blob/55823ba3b07f3a3dc80ec4bb010c2fceb5338c62/shared-bindings/keypad/ShiftRegisterKeys.c#L49C1-L58C111 Says:

//|         Create a `Keys` object that will scan keys attached to a parallel-in serial-out shift register
//|         like the 74HC165 or CD4021.
//|         Note that you may chain shift registers to load in as many values as you need.
//|         Furthermore, you can put multiple shift registers in parallel and share clock and latch.
//|
//|         Key number 0 is the first (or more properly, the zero-th) bit read. In the
//|         74HC165, this bit is labeled ``Q7``. Key number 1 will be the value of ``Q6``, etc.
//|         With multiple data pins, key numbers of the next pin are sequentially to the current pin.
//|
//|         An `EventQueue` is created when this object is created and is available in the `events` attribute.

Can we replace:

With multiple data pins, key numbers of the next pin are sequentially to the current pin.

with something like:

Key numbers are sequenced such that there are key_count[0] values read from data[0], followed by key_count[1] values read from data[1], etc.

Also, can we add to:

//| :param Union[microcontroller.Pin, Sequence[microcontroller.Pin]] data: the incoming shift register data pin(s)

to get:

//| :param Union[microcontroller.Pin, Sequence[microcontroller.Pin]] data: the incoming shift register data pin(s). When one Microcontroller.Pin is given, it is equivalent to a single element sequence.

And add to:

//| :param Union[int, Sequence[int]] key_count: number of data lines to clock in (per data pin)

to get:

//| :param Union[int, Sequence[int]] key_count: number of data lines to clock in (per data pin). When one int is given, it is equivalent to a single element sequence.

I'm happy to do a PR for you, if you agree this is what it should say (or give me feedback).

[aseanwatson]

PR merged