New style for menu pages

[AngelaRemolina]

Summary

• A html file was created containing css styling for tags or hyperlinks to look like buttons in pages that contains toctrees.
• The course content was dived into 4 modules to shorten the menu options (before there were 41 options)
• A new zombie image was added from the original course in the 4 divisions index page.

This PR closes https://github.com/angelasofiaremolinagutierrez/PyZombis/issues/4

And also closes https://github.com/angelasofiaremolinagutierrez/PyZombis/issues/12

Checklist

• [x] Variables, functions and comments are translated to Spanish
• [x] Functions follow underscore notation
• [x] Spell check done & typos fixed
• [x] All python code is PEP8 compliant
• [x] Test coverage with Playwright implemented; locators are Pyhton code
• [x] Reviewers assigned (all peers & at least 1 mentor)

Screenshots

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Published to http://pyar.github.io/PyZombis/163/index.html

[github-actions[bot]]

Published to http://pyar.github.io/PyZombis/163/index.html

[github-actions[bot]]

Published to http://pyar.github.io/PyZombis/163/index.html

[github-actions[bot]]

Published to http://pyar.github.io/PyZombis/163/index.html

[github-actions[bot]]

Published to http://pyar.github.io/PyZombis/163/index.html