Use png version of cropped parabola

Create also a png version of the cropped parabola plot and use this version in
the README.

README.md

@@ -132,7 +132,7 @@ the cropped parabola f(x), which is limited y=4 for x>=2.
 ```
 
 The final plot should look like this.
-!(Plot of cropped parabola)[https://srv.sauerburger.com/esel/FP-python-examples/-/jobs/artifacts/master/raw/cropped_parabola.eps?job=doxec_test]
+![Plot of cropped parabola](https://srv.sauerburger.com/esel/FP-python-examples/-/jobs/artifacts/master/raw/cropped_parabola.png?job=doxec_test)
 
 Create the file `func_plot.py` and add the following lines.
 
@@ -180,6 +180,12 @@ plt.xlabel("$x$")  # latex synatx can be used
 plt.ylabel("cropped parabola")
 plt.savefig("cropped_parabola.eps")
 ```
+<!-- append func_plot.py
+```python
+# We need also a png version of the plot to embed it into the README.md.
+plt.savefig("cropped_parabola.png")
+```
+-->
 
 Run your script and check the file `cropped_parabola.eps` is created.
 <!-- console -->
@@ -191,6 +197,8 @@ $ python3 func_plot.py
 ```
 $ ls cropped_parabola.eps
 cropped_parabola.eps
+$ ls cropped_parabola.png
+cropped_parabola.png
 ```
 -->