adopt custom template

Author: parmentelat

notebooks/myst.yml

@@ -28,7 +28,8 @@ project:
     output_matplotlib_strings: warn
 
 site:
-  template: book-theme
+  #template: book-theme
+  template: https://github.com/flotpython/myst-theme/releases/download/custom/book.zip
   # used in the tab name
   title: programmer en Python
   # this would be for the horizontal header bar - not used here (yet)