feat: Add multi-sensor reaction game example.

[nedseb]

What

Create a reaction game that randomly asks the player to perform different actions using various sensors and the D-PAD, then measures response time.

Why

Fun way to combine multiple STeaMi drivers in a single interactive example. Teaches event-driven programming and sensor polling.

Suggested approach

1. The OLED displays a random command:
   • "TILT LEFT" → check ISM330DL accelerometer X axis
   • "PRESS UP" → check MCP23009E D-PAD
   • "COVER SENSOR" → check APDS9960 ambient light drops below threshold
   • "BLOW" → check HTS221 humidity spike
2. Start a timer with ticks_ms()
3. Wait for the correct sensor to trigger (with a 5-second timeout)
4. Display reaction time on the OLED + play a success/fail buzzer sound
5. After 10 rounds, show the average reaction time as the final score

Hardware

• SSD1327 OLED + buzzer
• ISM330DL, MCP23009E (D-PAD), APDS9960, HTS221

Documentation

Write a pedagogical activity sheet for the STeaMi wiki covering:

• Learning objectives (sensors, polling, timing, game design)
• Step-by-step instructions for students
• Expected behavior and scoring
• Extension ideas (add more actions, difficulty levels, multiplayer via BLE)

[nedseb]

Cross-reference with Arduino: steamicc/arduino-steami-lib#74 proposes a similar ReactionTimer example in Arduino. Once the MicroPython version is done, the design and logic can be reused for the Arduino port.