[Readme] missing one command to host website locally

When we run website locally with mentioned instructions in readme file.it just build project only but does not deploy it on locally in browser.On terminal we need some other instruction also to run website locally on browser also.

With **npm run build** it just build the project but does not deploy it on browser locally.
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**This is what happens after installing all dependencies but it just build project not host it locally on browser**

從 README 中 `npm run build` 附近的說明開始，驗證執行該命令後會發生什麼。找出專案中缺少的、用於在瀏覽器中進行本機服務的步驟，然後更新 README，以便記錄完整的建置與託管工作流程，並能夠成功執行。

由索引模型根據 Issue 內容生成。