Fixed bug due to change in githubs ui

📑 Description
These changes apply the user-requested dark-theme detection method, using the browser's preferences.
I also fixed a pending bug with how fallback popups work in firefox and extended its functionality to allow for separation of concerns in css styling.

Fixed
• Toolbar not appearing on the first inline comment in GitHub’s new review UI.
Previously, our extension only detected the “new” GitHub review experience after at least one comment existed (due to relying on div[data-testid="review-thread"]). As a result, the toolbar didn’t load for the very first comment box.

Changes
• Improved GitHub experience detection
• Added support for new UI markers that exist before any comments are created:
• div[data-marker-navigation-new-thread="true"]
• div[data-marker-id]
• [class^="MarkdownEditor-module__container"]
• textarea[aria-label="Markdown value"]
• Ensures we now recognize the new review experience even when a PR has no comments.
• Updated textarea selectors for GitHub new UI
• Removed brittle, hashed class selectors (e.g., .prc-Textarea-TextArea-*).
• Replaced with robust, stable selectors:
• First inline editor:
div[data-marker-navigation-new-thread="true"] textarea[aria-label="Markdown value"]
• Any inline thread editor:
div[data-marker-id] textarea[aria-label="Markdown value"]
• Fallback for PR header/new comment boxes:
fieldset textarea[aria-label="Markdown value"]

Result
• The toolbar now appears correctly on the very first comment box in GitHub PRs, matching behavior for subsequent comment boxes.

New Features

• Added support links in extension settings popup
• Enhanced dark/light theme support across all extension popups

Improvements

• Improved logo carousel animation with smoother scrolling
• Enhanced extension popup styling and layout consistency

Bug Fixes

• Resolved logo visibility issues in different themes
• Fixed extension popup styling inconsistencies