Teensytoany

* added function `spi_read_byte` enabling the user to read SPI register.

* added function `analog_read` enabling the user to read analog signals.

* added `i2c_read_payload and` `i2c_write_payload functions` which allows users to read and write a contiguous payload of bytes

* `gpio_pin_mode` now takes an optional parameter to set the value after the
mode is set. This is useful for those setting output pins to avoid any delay
in the serial communication that could set the pins in an invalid state
for a lengthy period of time.

* Add new command `gpio_digital_pulse` and `gpio_digital_pulse_us` that enable
the use to pulse a digital pin.

* Add new command `analog_pulse` that enable the use to pulse a an analog pin
at a given duty cycle.

* `spi_transfer_bulk` now also returns the data read back from device.

* Add the command `i2c_read_payload_no_register` to provide the ability to read
from devices like the AT24CS01 EEPROM data over I2C.
* Add the command `i2c_read_payload_uint16`.

* Add support for I2C on the Teensy4 through the use of
[Richard Gemmell's library](https://github.com/Richard-Gemmell/teensy4_i2c/).