Add date to logs to files

Not sure why it's not there. Since the file name don't have date on
them, it's better to at least have the date there.

config/config.exs

@@ -104,17 +104,17 @@ config :logger, LoggerBackends.Console,
   level: :debug
 
 config :logger, :error_log,
-  format: "$time [$level] $metadata $message\n",
+  format: "$date $time [$level] $metadata $message\n",
   metadata: metadata,
   level: :error
 
 config :logger, :notice_log,
-  format: "$time [$level] $metadata $message\n",
+  format: "$date $time [$level] $metadata $message\n",
   metadata: metadata,
   level: :notice
 
 config :logger, :info_log,
-  format: "$time [$level] $metadata $message\n",
+  format: "$date $time [$level] $metadata $message\n",
   metadata: metadata,
   level: :info