upload README.md for each chapter

Author: rebuild-123

observer/simple/README.md

@@ -0,0 +1,5 @@
+## Execute the main file with the below command.
+ ```python3
+python Example.py
+ ``` 
+![image](https://github.com/rebuild-123/Python-Head-First-Design-Patterns/blob/main/pictures_for_README/observer_simple.png)

observer/simpleobservable/README.md

@@ -0,0 +1,5 @@
+## Execute the main file with the below command.
+ ```python3
+python Example.py
+ ``` 
+![image](https://github.com/rebuild-123/Python-Head-First-Design-Patterns/blob/main/pictures_for_README/observer_simpleobservable.png)

observer/weather/README.md

@@ -0,0 +1,6 @@
+## Execute the main file with the below command.
+ ```python3
+python WeatherStation.py
+python WeatherStationHeatIndex.py
+ ``` 
+![image](https://github.com/rebuild-123/Python-Head-First-Design-Patterns/blob/main/pictures_for_README/observer_weather.png)

observer/weatherobservable/README.md

@@ -0,0 +1,6 @@
+## Execute the main file with the below command.
+ ```python3
+python WeatherStation.py
+python WeatherStationHeatIndex.py
+ ``` 
+![image](https://github.com/rebuild-123/Python-Head-First-Design-Patterns/blob/main/pictures_for_README/observer_weatherobservable.png)