mosquitto egg - minor suggestions for the example

The example has a call to string->append. I'm guessing this is a typo? I
suggest replacing the display calls with print or adding a newline. When
running the example the screen output can get buffered and not show up for
a long time which might be confusing.

Aside 1:

The mosquitto egg is a great example of just how rewarding it is to use
Chicken Scheme. So thank you to the 25 years from Felix and the developers
and to all the egg makers including Dmitrii who made the mosquitto egg!

Aside 2:

Just for anyone who might find it interesting, here are a few details on
the project I just did where I was able to use Chicken.

When there are prolonged periods of rain our basement can get water
ingress. There is an old and unused well 10m from the house. I peeked in
that well and to my surprise the water was at less than 2m from the
surface. High enough to be possibly related to the water ingress. I thought
I'd try to lower the water table and see if that impacts the basement water
problem. I setup a 12v well pump, solar panel, LiFePo4 battery, esp32 relay
board and a water level sensor so that the pump runs for 3 minutes (enough
to fill a 5gal/20l bucket) when the level sensor detects water. The esp8266
connects via wifi to wireless using mqtt and a chicken scheme program logs
the pump runs in an sqlite3 db. The first three weeks it was pumping about
300-400l a day then a couple days ago it dropped to 40l day. We haven't had
any long periods of rain so I don't know if the project will actually solve
the basement issue but I was so pleased to be able to use Chicken for the
datalogging portion that I thought I'd write this up.

Cheers,
Matt
-- 
“Reality is that which, when you stop believing in it, doesn’t go away” -
Philip K. Dick