split code up into modules and add pubsub and timers

CIRCUITPY/weather_station/timer.py

@@ -0,0 +1,10 @@
+class Timer:
+    def __init__(self, pubsub, timer_length):
+        self.timer_length = timer_length
+        self.last_tick = 0
+        self.pubsub = pubsub
+        self.topic = f"tick {self.timer_length}"
+    def tick(self, now):
+        if (now - self.last_tick) > self.timer_length:
+            self.last_tick = now
+            self.pubsub.publish(self.topic, {})