Unity provides constants that reflect the maximum value of integer types,
use it for checking the checksum overflow rather than using 65536 directly.
This makes the intent more clear.
The Arduino will block if sent data too quickly after connection.
Add a new coroutine to force waiting for 1s+ and update the UI
accordingly.
Update some comments throughout.
Add the full working Arduino code for cart loading.
Handle the UI elements, connection to the Arduino
and loading the cartridge over serial.
This code should not be shared with students as it
is the full working code for the communication.
