feat: Add weather face example with comfort display.

[nedseb]

What

Create an example that reads temperature, humidity and pressure, then displays a face expression on the OLED that reflects indoor comfort (happy = ideal, sad = cold, angry = hot).

Why

Natural extension of the tamagotchi (#399). Combines sensor readings with the `steami_screen.face()` widget for an expressive, easy-to-understand output.

Suggested approach

1. Read temperature from WSEN-PADS, humidity from HTS221
2. Evaluate comfort:
   • 18-26°C and 40-60% RH → `screen.face("happy")` + "IDEAL"
   • Too hot (>30°C) or humid (>75%) → `screen.face("angry")` + "HOT"
   • Too cold (<15°C) or dry (<25%) → `screen.face("sad")` + "COLD"
3. Display the face + temperature + humidity values using `steami_screen` widgets
4. Update every second
5. `try/finally` with `power_off()` for both sensors

Hardware

• SSD1327 OLED
• WSEN-PADS (temperature + pressure)
• HTS221 (humidity)

Documentation

Write a pedagogical activity sheet for the STeaMi wiki covering:

• Learning objectives (sensors, comfort index, conditional logic, UI feedback)
• Step-by-step instructions
• How to test (blow warm air, move to cold room, etc.)
• Extension ideas (add pressure trend, historical graph, BLE broadcast)

[nedseb]

Cross-reference with Arduino: steamicc/arduino-steami-lib#93 has a related ClimateDisplay example (HTS221 + bar graphs). The Arduino version could be enriched with an expressive face like this MicroPython one — see steamicc/arduino-steami-lib#100 for the follow-up.