Add link to Pangeo on landing page

landing-page.md

@@ -0,0 +1,9 @@
+# Pythia Foundations
+
+## A community learning resource for Python-based computing in the geosciences
+
+<img src="images/pretty-earth.png" alt="Pretty Earth" width="600px">
+
+This collection covers the foundational skills everyone needs to get started with scientific computing in the open-source Python ecosystem.
+
+<img src="images/logos/ProjectPythia_Logo_Final-01-Blue.svg" alt="Project Pythia logo" height="80px"> _Brought to you by [Project Pythia](https://projectpythia.org), the education working group for [Pangeo](https://pangeo.io)_ <img src="https://raw.githubusercontent.com/pangeo-data/pangeo/master/docs/_static/small_e_logo_cropped.png" alt="Pangeo logo" height="80px">

preamble/how-to-use.md

@@ -45,7 +45,7 @@ Notebook](https://jupyterbook.org/intro.html) “chapters”. The power
 of Jupyter Notebooks is that they can contain both static text and
 executable code that you can interact with. When you navigate to a
 book chapter such as [Matplotlib
-Basics](https://foundations.projectpythia.org/core/matplotlib/matplotlib.html)
+Basics](../core/matplotlib/matplotlib-basics)
 you will see static text, Python code, and the rendered output of
 that code in the form of the many figures that appear. In the case
 of Matplotlib Basics these figures are produced by Matplotlib itself.