split code up into modules and add pubsub and timers

CIRCUITPY/weather_station/pubsub.py

@@ -0,0 +1,16 @@
+class PubSub:
+    def __init__(self):
+        self.cbs = {}
+    def _check_msg_type(self, msg_type):
+        if msg_type not in self.cbs:
+            self.cbs[msg_type] = []
+
+    def subscribe(self, msg_type, cb):
+        self._check_msg_type(msg_type)
+        self.cbs[msg_type].append(cb)
+
+    def publish(self, msg_type, body):
+        self._check_msg_type(msg_type)
+        print(f"publishing msg {msg_type}")
+        for cb in self.cbs[msg_type]:
+            cb(body)