doc: Introduce way to install also dependencies

doc/doc-installation.md

@@ -19,6 +19,12 @@ cd pyicon
 pip install -e .
 ``` 
 
+For a more complete installation that includes dependencies for testing, 
+debugging and compiling the documentation use:
+```
+pip install -e .[full]
+```
+
 ### On an arbitrary system
 
 pyicon is developed for python 3.8 or later. Other versions might work as well but are not supported so far.
@@ -37,6 +43,12 @@ cd pyicon
 pip install -e .
 ```
 
+For a more complete installation that includes dependencies for testing, 
+debugging and compiling the documentation use:
+```
+pip install -e .[full]
+```
+
 The above instructions will provide a minimum python environment that will be sufficient for most applications. 
 However, some more advanced features might require the installation of further python packages.
 For a complete list of python packages that is supposed to cover all aspects can be obtained from the latest