Add footer with Game Off '25 credits

[Copilot]

Adds a footer at the bottom of the page with credits for GitHub Game Off '25, creator and Copilot attributions, and source link.

Changes

• HTML structure: Added <footer> element with links to Game Off '25, @leereilly, @copilot, and repository
• Layout: Changed body flexbox to flex-direction: column to stack game and footer vertically
• Styling: Small text (12px), subtle gray (#8b949e), GitHub blue links (#58a6ff), centered with 20px top margin

<footer>
    Made with ♥ for <a href="https://itch.io/jam/game-off-2025">GitHub Game Off '25</a> by 
    <a href="https://github.com/leereilly">@leereilly</a> &amp;&amp; 
    <a href="https://github.com/copilot">@copilot</a> · 
    <a href="https://github.com/leereilly/commit-dash">View source</a>
</footer>

Screenshot

Original prompt

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This section details on the original issue you should resolve

<issue_title>:copilot: Add a footer</issue_title>
<issue_description>Add the world's sexiest footer to the bottom of the screen reading,

Made with ♥ for GitHub Game Off '25 by @leereilly && @copilot · View source

Keep the design minimal, clean, and aligned with the game’s aesthetic (small text, subtle color, centered).</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add a footer #3

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[leereilly]

For the link color, please match the lightest green hex color of the green squares, @copilot.