feat: add announcement bar with updated gittogether details

[amaan-bhati]

Added a custom sticky announcement experience for GitTogether SF using the swizzled Docusaurus announcement bar.

What changed

• Added a sticky announcement bar above the navbar for event promotion.
• Kept the desktop and mobile layouts responsive, including CTA and dismiss controls.
• Added marquee highlights with hover-to-pause behavior and click-through navigation to the event page.
• Wired the bar into Docusaurus announcement bar state so dismissal respects the configured announcement id and persists across navigation/reload.
• Updated header offsets so sticky navbar, breadcrumbs, and anchor scroll positions account for the announcement height consistently.
• Switched the visual treatment to use a repo-shipped image asset instead of an external runtime dependency.

Configuration

• Announcement copy, id, and closeability are configured through themeConfig.announcementBar in docusaurus.config.js.
• The bar can be disabled by removing themeConfig.announcementBar from the config.

[Copilot]

Pull request overview

Adds a custom, Tailwind-styled Announcement Bar featuring a marquee message and CTA for updated GitTogether SF event details.

Changes:

• Added a custom src/theme/AnnouncementBar implementation with marquee animation, swipe-to-dismiss behavior, and a CTA link.
• Extended Tailwind config with marquee keyframes/animation.
• Updated global CSS to make the navbar sticky beneath the announcement bar and stripped default Docusaurus announcement bar styling.
• Updated docusaurus.config.js announcement bar id/content.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 7 comments.

File	Description
tailwind.config.js	Adds marquee keyframes and animate-marquee utility used by the new announcement bar.
src/theme/AnnouncementBar/index.js	Introduces the new announcement bar UI (marquee, CTA, dismiss interactions) and height syncing to a CSS variable.
src/css/custom.css	Makes navbar sticky below the bar via --docusaurus-announcement-bar-height; removes default Docusaurus announcement bar styling.
docusaurus.config.js	Updates announcement bar id/content for the GitTogether SF messaging.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 4 changed files in this pull request and generated 8 comments.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated 2 comments.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated 3 comments.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated no new comments.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

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[Copilot]

Pull request overview

Copilot reviewed 4 out of 5 changed files in this pull request and generated no new comments.

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