Update README.md

Author: akoutmos

README.md

@@ -108,10 +108,13 @@ defmodule MyCoolApp.Application do
 
   def start(_type, _args) do
     children = [
-      MyAppWeb.Endpoint,
-      # PromEx should be started after the Endpoint, to avoid unnecessary error messages
+      # PromEx should be started before anything else as PromEx will caputre init events from
+      # libraries like Ecto, Phoenix and Oban. If it is started after those other supervision trees
+      # you will miss those events and metrics.
       MyCoolApp.PromEx,
 
+      MyCoolApp.Repo,
+      MyCoolApp.Endpoint
       ...
     ]