Add support for STM32 which is using TwoWire.h

[TylerBird]

Subject of the issue

Since version 1.0.2 define options for the I2C_BUFFER_LENGTH_RX and _TX are added, this is now causing in a problem for my use of this library in combination with the STM32.

In file included from lib\24LC64/24LC64.h:5,
                 from src\main.h:5,
                 from src\main.cpp:1:
.pio\libdeps\disco_l072cz_lrwan1\SparkFun External EEPROM Arduino Library\src/SparkFun_External_EEPROM.h:59:19: error: This platform doesn't have a wire buffer size defined. Please contribute to this library! 
   59 | #pragma GCC error "This platform doesn't have a wire buffer size defined. Please contribute to this library!"
      |                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Your workbench

• STM32
• LoRa ST (EU868)
• Wired via I2C
• Power Supply is 3V3
• I'm using PlatformIO

Steps to reproduce

It would be nice if there is either the possibility to define this in your own code via a general define which has to be added even without a specifically selected controller, or by supporting the STM32 also.
Currently I also use the Wire.h so in my Code the BUFFER_LENGTH is defined.

Possible changes:

#elif defined(__AVR_ATmega328P__) || defined(__AVR_ATmega168__) || defined(STM32)

or:

#elif defined(STM32)

#define I2C_BUFFER_LENGTH_RX BUFFER_LENGTH //BUFFER_LENGTH is defined in Wire.h
#define I2C_BUFFER_LENGTH_TX BUFFER_LENGTH

Expected behavior

Not running into the else part and getting the pragma GCC error

Actual behavior

Running into the else part for defining the I2C_BUFFER_LENGTH_RX and _TX.

[TylerBird]

I'm not absolutly sure if my suggestions are solving my problem correctly.
It looks like I need to define that specifically for it.
Is that the intention?

[TylerBird]

Ok, the second suggetion is working for me.
I will make a merge request for adding STM32 as shown above.