RowColumnScanning tutorial omits resistors [MKC-555]

The tutorial at https://www.arduino.cc/en/Tutorial/RowColumnScanning omits resistors in driving the LEDs. There is a common misconception in the Arduino scene, that I/O pins are somehow (safely) current limited and need no resistors with LEDs, but this is not actually the case. It would be good if at least official Arduino documentation set the right example...

Open the RowColumnScanning tutorial at the linked Arduino documentation URL and inspect its LED-driving instructions and circuit example. Update the tutorial so the resistor requirement is shown clearly, then verify that the wiring guidance consistently demonstrates safe LED use.

Written by the indexing model from the issue text.