Add cleaning sen44 sensor after 2 days.

aqi.ino

@@ -59,6 +59,7 @@ struct {
     unsigned long on_off_btn = 0;
     unsigned long update_lcd = 0;
     unsigned long sen44      = 0;
+    unsigned long cleaning   = 0;
 } parallel;
 
 // Force write data to screen.
@@ -164,6 +165,12 @@ void loop(void)
         sen44_mes.temp = celsius_to_fahrenheit(sen44_mes.temp);
         sen44_mes.f_temp = heat_index(sen44_mes.temp, sen44_mes.hum);
     }
+
+    // "Parallel" execution for triggering cleaning in Sen44 after 2 days.
+    if (millis() - parallel.cleaning >= 172800000) {
+        parallel.cleaning = millis();
+        sen44.startFanCleaning();
+    }
 }
 
 // Write data to screen.