Fix dark theme toggle and HTML validation errors

[Copilot]

The site had a non-functional dark theme toggle button and several HTML validation errors.

Changes

• Dark theme CSS: Added .dark-theme class styles to match existing @media (prefers-color-scheme: dark) queries. The JavaScript was toggling the class but CSS had no corresponding rules.

• Theme toggle button: Added styles for #theme-toggle with border, hover states, and proper alignment in the navigation bar.

• HTML fixes: Corrected malformed closing tags (</p.strong> → </p>, </secton> → </section>, </span></a> → </a>).

• .gitignore: Added to exclude node_modules/, build artifacts, and editor files.

Implementation

The dark theme styles mirror the existing media query logic but apply when .dark-theme is present:

.dark-theme {
    --light-grey-ish: #b6b6b6;
    background-color: #1b1f23;
    color: var(--light-grey);
}

.dark-theme a {
    color: var(--light-grey);
}

Screenshots

Light theme:

Dark theme (toggle clicked):

The theme toggle (moon/sun icon, top right) now works correctly and persists preference to localStorage.

Original prompt

---

This section details on the original issue you should resolve

<issue_title>test</issue_title>
<issue_description>test</issue_description>

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

• Fixes test testio#8

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