NEO6502 startup
this is my initial take of getting the neo6502 memory emulator functionality working
09/07/2023 added a simple soundgenerator as experiment
10/07/2023 cleanup of keyboard processing
11/07/2023 BRK handler added (will display content of registers)
12/07/2023 Prepping for dynamic ROM loading mechanism & moved RESET(40) ==> UEXT.3 to free up SPI