docs: add official Pearipherals GitHub Pages website

[OnlineFix]

Summary

• Add a lightweight accessible static project website in /docs only: HTML/CSS, .nojekyll, robots.txt and sitemap.xml.
• Explain separate driver requirements, function keys, gestures, battery warnings, installation/removal and FAQ using current official documentation.
• Put the unsigned-beta security warning before the exact v1.2.1 release link; explicitly preserve hardware and testing limitations.
• Use the Pages API-confirmed canonical URL https://onlinefix.github.io/Pearipherals/.

Validation

• HTML5 strict parser passed; CSS parsed without errors; semantic metadata and internal anchors checked.
• All 15 unique external links returned HTTP 200 (issue submission redirects to GitHub sign-in as expected); documentation fragments verified.
• No JavaScript, remote fonts, analytics, cookies, application source changes or workflow edits.
• Existing CI verify must pass before merge; public Pages content and deployed SHA will be checked after merge.

Publication scope

GitHub Pages is configured for main /docs using GitHub-managed branch deployment and HTTPS. No custom workflow, secrets, paid hosting, app builds or releases are introduced. Search indexing and ranking are not guaranteed.