Create two links to code snippets for students

[lauracumming]

Summary
Teachers have responded and informed us that they think that linking to our code to demonstrate python concepts will boost understanding and learning. We would like to add two links to the new Python Den to test these out. Let's start with Selection and Iteration.

User story
The user story that has led to the need for this task, expressed in the format below.
_As a student or teacher
_I would like to provide and example that relates to the game
_so that the students can understand their learning in a real world example.

Outcome/deliverable
Collate the text and images in a doc, so that it can then go into design

Deadline
tbc

Links
tbc

Reviewer
@rdcruzCFL

People to contact
@lauracumming