feat: Webサイトに全文検索を実装

[3w36zj6]

close https://github.com/typst-jp/typst-jp.github.io/issues/142

確認事項

• SP, PCサイズの画面で検索機能が利用できる

[Copilot]

Pull Request Overview

This PR implements a full-text search feature on the website through pagefind integration.

• Adds a new SearchWindow component and exports it through the common UI index.
• Integrates search functionality into both the Header and BaseTemplate for a consistent search modal.
• Updates build scripts and documentation to generate the search index using pagefind.

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
website/src/components/ui/common/index.ts	Exports the new SearchWindow component.
website/src/components/ui/common/SearchWindow.tsx	Implements the search window with pagefind integration.
website/src/components/ui/common/Header.tsx	Adds search buttons with the new SearchIcon.
website/src/components/templates/BaseTemplate.tsx	Integrates searchOpen state and modal rendering for SearchWindow.
website/src/components/icons/index.ts	Exports the new SearchIcon component.
website/src/components/icons/SearchIcon.tsx	Implements the search icon component.
website/package.json	Updates build commands and adds the pagefind dependency.
website/README.md	Documents instructions for full-text search testing.

[kimushun1101]

SP、PCで検索機能を確認できました。

export VITE_LISTEN_ALL_ADDRESSES=true
mise run generate
# mise run dev # READMEにあるようにこれでは検索機能は使えない
mise run preview

確認ですが、ひとまずこのPRでは以下の状態でよろしいでしょうか？
私としては困っていないため大丈夫です。

• bun run devで動かせない。
• bun run buildで以下のメッセージがでています。

  Note: Pagefind doesn't support stemming for the language ja. 
  Search will still work, but will not match across root words.
  

[gomazarashi]

検索機能が問題なく利用できることを確認しました。

[3w36zj6]

Note: Pagefind doesn't support stemming for the language ja.
Search will still work, but will not match across root words.

こちらの詳細はドキュメントのMultilingual searchに書かれています。

https://pagefind.app/docs/multilingual/#language-support