feat(recipe): add customization of build file names recipe

[casungo]

Description (required)

This pull request introduces a new recipe page to the Astro documentation titled "Customizing Output File Names."

This recipe addresses the need for users to have more control over the naming and directory structure of their built assets (JavaScript, CSS, images, fonts, etc.). It explains how to leverage Vite's Rollup output options within the astro.config.mjs file to customize entryFileNames, chunkFileNames, and assetFileNames.

This content was previously part of the v4 documentation but was removed from the main configuration page as it's considered a more advanced use case. Creating it as a recipe makes this valuable information accessible to users who specifically need this customization, as suggested in issue #10348.

Related issues & labels (optional)

• Closes #10348
• Suggested label: recipe, add new content