Python guide: include code examples using Jekyll

[gkunz]

One objective of the Python guide is to provide executable code examples in separate Python scripts. At the same time, the code examples should also be shown in listings in the guide.

Problem: Markdown itself does not allow to include other files, i.e., such as the code examples.

Proposal: To avoid duplicating the code of the scripts in the markdown files, we can use Jekyll's include_relate primitive [1] to include the scripts in the rendered guide.

Specifically, this pattern seems to work:

```python
{% include_relative compliant01.py %}
```

[1] https://jekyllrb.com/docs/includes/#including-files-relative-to-another-file

cc @myteron @tommcd

[myteron]

Gut feeling tells me that Jekyll appears to me a little to flexible with a potential for injection via variables. Haven't tried. Editing requires to compile and run a web-server. Was somewhat hoping for a more simplistic solution.

[gkunz]

Jekyll is run under the hood by GitHub when rendering the current guides.

I run a test using my fork:

• Code: https://github.com/gkunz/wg-best-practices-os-developers/blob/0afa4264397698051ee0be84f219a34cf73c8f46/docs/Secure-Coding-Guide-for-Python/CWE-664/CWE-134/README.md?plain=1#L19

• Resulting render (notice that the first example appears twice: https://gkunz.github.io/wg-best-practices-os-developers/docs/Secure-Coding-Guide-for-Python/CWE-664/CWE-134/