feat(download): add asdf install method

[Herrtian]

Description

Adds asdf as a Community install method on the downloads page, with an English snippet and no custom icon.

Validation

• corepack pnpm prettier
• corepack pnpm --filter @node-core/website lint:js
• corepack pnpm --filter @node-core/ui-components lint:js
• corepack pnpm --filter @node-core/ui-components lint:css
• corepack pnpm --filter @node-core/website lint:types
• corepack pnpm --filter @node-core/ui-components lint:types
• corepack pnpm --filter @node-core/website test:unit -- util/__tests__/download.test.mjs
• corepack pnpm --filter @node-core/ui-components test
• corepack pnpm --filter @node-core/website build

Related Issues

Fixes #8488

Check List

• I have read the Contributing Guidelines and made commit messages that follow the guideline.
• I have run pnpm format to ensure the code follows the style guide.
• I have run pnpm test to check if all tests are passing.
• I have run pnpm build to check if the website builds without errors.
• I've covered new added functionality with unit tests if necessary.

[vercel]

The latest updates on your projects. Learn more about Vercel for GitHub.

Project	Deployment	Actions	Updated (UTC)
nodejs-org	Ready	Preview	May 28, 2026 11:40am

[cursor]

PR Summary

Low Risk
Downloads-page content and UI only; no auth, data, or build pipeline changes beyond optional icon handling.

Overview
Adds asdf as a community install option on the downloads page for macOS and Linux, with a new bash snippet (plugin add, install, global set) and copy in the code box.

Wires it through InstallationMethod, installMethods in constants (no custom icon), and an English platformInfo.asdf string. createIcon now treats a missing or unknown icon as optional so methods without an icon still render in the dropdown.

^{Reviewed by Cursor Bugbot for commit 738d649. Bugbot is set up for automated code reviews on this repo. Configure here.}

[AugustinMauroy]

Why theses changes ?

[Herrtian]

Removed this CSS change; it was not needed for adding asdf.