Add SPI to ArduinoFake

[rcalcover]

Hi I am trying to add SPI Arduino Core library and contribute in ArduinoFake for the community.
I have followed the contribution guidelines and added SPI the same way as the Print since its quite similar to it. The issue was that I encountered an error that I was stuck on ArduinoFake.h:

                 from test/main.cpp:1:
src/ArduinoFake.h: In member function ‘SPIClassFake* ArduinoFakeContext::SPIClass(SPIClass*)’:
src/ArduinoFake.h:59:52: error: cannot dynamic_cast ‘instance’ (of type ‘class SPIClass*’) to type ‘class SPIClassFakeProxy*’ (source type is not polymorphic)
         if (dynamic_cast<name##FakeProxy*>(instance)) { \
                                                    ^
src/ArduinoFake.h:103:9: note: in expansion of macro ‘_ArduinoFakeInstanceGetter2’
         _ArduinoFakeInstanceGetter2(SPIClass, SPIClass)
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~
src/ArduinoFake.h:60:59: error: cannot dynamic_cast ‘instance’ (of type ‘class SPIClass*’) to type ‘class SPIClassFakeProxy*’ (source type is not polymorphic)
             return dynamic_cast<name##FakeProxy*>(instance)->get##name##Fake(); \
                                                           ^
src/ArduinoFake.h:103:9: note: in expansion of macro ‘_ArduinoFakeInstanceGetter2’
         _ArduinoFakeInstanceGetter2(SPIClass, SPIClass)` 

It showed when I added _ArduinoFakeInstanceGetter2(SPIClass, SPIClass) on ArduinoFakeContext.