Add DJ timer to 'dj' command output

Specifically, store 'broadcast_start' from the AzuraCast API, and use that + current time to calculate how long the DJ has been streaming for.

tilderadio.py

@@ -88,6 +88,7 @@ class Module(ModuleManager.BaseModule):
         # self.song = data["now_playing"]["song"]["text"]
         self.is_online = data["live"]["is_live"]
         self.dj = data["live"]["streamer_name"]
+        self.broadcast_start = data["live"]["broadcast_start"]
         #self.listeners = data["listeners"]["current"]
 
     def format_nowplaying(self):
@@ -289,6 +290,10 @@ class Module(ModuleManager.BaseModule):
             message = "no one is currently on the air"
         else:
             message = f"{self.dj} is now streaming!"
+            if self.broadcast_start:
+                now = utils.datetime.utcnow().timestamp()
+		total_seconds = now - self.broadcast_start
+		message += " (for {})".format(util.datetime.to_pretty_time(total_seconds))
         event["stdout"].write(message)
 
     @utils.hook("received.command.slogan")