Update GitHub Codespaces instructions for S2L5

[ariyonaty]

Summary

Hello Maintainers!

First and foremost, thank you for Secure Code Game. It was a blast, learned a ton, and love the idea and motivation behind it.

This PR fixes and enhances a documentation issue for Season 2, Level 5 for Codespace users. While current documentation provides instructions for index.html, it is lacking for code.js, which is required. See Issue #84 for additional context.

This PR pivots the solution slightly by proposing changes which achieve same outcome for Codespace users without having to pull/copy files locally.

Changes

BLUF: Leverage Python http.server to serve directory via Codespace.

Rather than copy both index.html and code.js to local environments, documentation updated to run simple HTTP web server within the codespace and allow user to remain within the same environment.

Screenshot verifying expected behavior:

Additional change - ensure character encoding set to utf-8 to avoid issue with rendering the dollar-sign graphics.
Before/After screenshot:

Closes: #84

Task list

• For workflow changes, I have verified the Actions workflows function as expected.
• For content changes, I have reviewed the style guide.