Added pip3 for matplotlib.

doc/erko_howto_tools.txt

@@ -883,6 +883,7 @@ Start --> Administration --> Synaptic package manager
 > sudo -s   # to become root
 > sudo pip install numpy      # to run Python2 library installer as root
 > sudo pip3 install numpy     # to run Python3 library installer as root
+> sudo pip3 install matplotlib
 
 > sudo apt-get install python3-tk # worked, now I can do: python3 test_plot.py
 
@@ -909,6 +910,8 @@ Start --> Administration --> Synaptic package manager
 # Add to .bashrc: export PATH="$HOME/.local/bin:$PATH"
 > jupyter-lab
 
+WARNING: The scripts f2py, f2py3 and f2py3.8 are installed in '/home/kooistra/.local/bin' which is not on PATH.
+
 # Markdown
 > sudo pip3 install markdown  # zit al in Python3, maar kan alleen md --> html
 > sudo pip3 install mdutils   # https://pypi.org/project/mdutils/ # kan md genereren