Merge pull request #40 from EXP-code/The9Cat-patch-1

Add nbsphinx-link to installation instructions

Author: The9Cat

README.rst

@@ -16,14 +16,18 @@ install it along with the ReadTheDocs theme, run the following commands:
 
    pip install sphinx
    pip install sphinx-rtd-theme
+   pip install nbsphinx-link
 
 For a Linux system with `apt` (e.g. Ubuntu), you can do:
 
 ::
 
    apt-get install python3-sphinx python3-sphinx-rtd-theme
 
+   Note: The `nbsphinx-link` package is needed to process Python notebook examples 
+         but is not available via apt. It may be installed using pip:
 
+       pip install nbsphinx-link
 
 Compile the documentation
 -------------------------