add SPI support and example

[FoamyGuy]

This relies on the changes from: adafruit/Adafruit_CircuitPython_Register#59 So that should be merged before this is.

Adds SPI support by using new functionality pending addition to adafruit_register

This should be a major version bump if merged because the class name changed from the bus specific SPA06_003_I2C to the now generic SPA06_003.

Tested successfully with both SPI and I2C on Adafruit CircuitPython 10.0.0-beta.3 on 2025-08-29; Adafruit Feather RP2040 with rp2040

[FoamyGuy]

Note: this should bump to 2.0.0 when released because the class name change from SPA06_003_I2C -> SPA06_003 will cause old code using new library to break.

[tannewt]

One question about what the new constructor args should be.

You could also make a function that looks like the old class SPA06_003_I2C() and does the I2CDevice wrapping. It should probably have a deprecation warning though too.

[FoamyGuy]

The latest commit has over_spi(spi, cs) and over_i2c(i2c, address) functions that can be used to create the driver using the specified bus type. Examples are updated to use those new functions.

[tannewt]

A couple minor things. Definitely getting close. Thanks!

[tannewt]

Do we still need a class? Or can this be a function?

Also, please use the warnings module. I believe most CP builds will have it.

[FoamyGuy]

I changed this to a function and use warnings module in the latest commit.

Thank you

[tannewt]

Looks good to me! Thank you!