Adds 404 page

[WayneFerrao]

AB#52118

Description

This PR adds a 404 page matching the website's existing styling.

[Copilot]

Pull request overview

Adds a custom Docusaurus 404 (Not Found) page for the docs site, styled to match existing Fluid Framework website visuals.

Changes:

• Added a swizzled NotFound theme component rendering a custom 404 layout and “Back to Home” call-to-action.
• Added dedicated CSS for 404 page layout/typography/button styling.

Reviewed changes

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

File	Description
docs/src/theme/NotFound.tsx	New Docusaurus theme override that renders the custom 404 page content.
docs/src/css/notFound.css	New styling for the 404 page (layout, typography, and CTA link/button).

[Copilot]

The description text color is hard-coded. Since this site already defines theme-aware muted colors in custom.scss, consider using a CSS variable here (or introducing a --ffcom-muted-text-color) so the value stays consistent across components and themes.

[Copilot]

Dark-mode override uses a hard-coded hex color. Consider using a shared theme variable (or a dedicated --ffcom-muted-text-color override under [data-theme="dark"]) to avoid duplicating color values across the codebase.

Suggested change

	color: #666c77;
	max-width: 480px;
	margin-bottom: 2rem;
	}
	[data-theme="dark"] .ffcom-not-found-description {
	color: #748497;
	color: var(--ffcom-muted-text-color, #666c77);
	max-width: 480px;
	margin-bottom: 2rem;
	}
	[data-theme="dark"] {
	--ffcom-muted-text-color: #748497;

[Copilot]

.ffcom-not-found-link { text-decoration: none; } will likely be overridden by the global rule main a { text-decoration: underline; } (higher selector specificity). As a result, the “Back to Home” link may still render underlined in the default state. Consider increasing specificity (e.g., scope the selector under .ffcom-not-found / main.ffcom-not-found) or otherwise overriding the main a rule for this link style.

[github-actions]

🔗 No broken links found! ✅

Your attention to detail is admirable.

linkcheck output

> fluid-framework-docs-site@0.0.0 ci:check-links /home/runner/work/FluidFramework/FluidFramework/docs
> start-server-and-test "npm run serve -- --no-open" 3000 check-links

1: starting server using command "npm run serve -- --no-open"
and when url "[ 'http://127.0.0.1:3000' ]" is responding with HTTP status code 200
running tests using command "npm run check-links"


> fluid-framework-docs-site@0.0.0 serve
> docusaurus serve --no-open

[SUCCESS] Serving "build" directory at: http://localhost:3000/

> fluid-framework-docs-site@0.0.0 check-links
> linkcheck http://localhost:3000 --skip-file skipped-urls.txt

Crawling...

Stats:
  257792 links
    1822 destination URLs
    2063 URLs ignored
       0 warnings
       0 errors

[Josmithr]

Docs please :D