Missing USB Keyboard and Mouse support

The USB keyboard and mouse examples do not build for RP2040 based boards with the error:

```
In file included from /Applications/Arduino.app/Contents/Java/examples/09.USB/Keyboard/KeyboardMessage/KeyboardMessage.ino:23:0:
/Applications/Arduino.app/Contents/Java/libraries/Keyboard/src/Keyboard.h:25:10: fatal error: HID.h: No such file or directory
#include "HID.h"
^~~~~~~
compilation terminated.
exit status 1
Error compiling for board Arduino Nano RP2040 Connect.
```

Is this feature expected to work?

Start with the USB Keyboard and Mouse examples, especially KeyboardMessage.ino, and inspect Keyboard.h and the missing HID.h include shown in the compiler output. Determine whether these examples are supported on Arduino Nano RP2040 Connect and document or resolve the build failure; done means the support status is clear and the examples build successfully if support is expected.

Written by the indexing model from the issue text.