docs(headless/install): add -D to install scripts

Author: maiieul

apps/website/src/routes/docs/headless/install/index.mdx

@@ -10,9 +10,9 @@ import qwikdevAstroCLI from '../../../../../public/images/qwikdev-astro-cli.webp
 import { ConfettiButton } from './confetti-button';
 
 export const packages = {
-  npm: 'npm install @qwik-ui/headless',
-  yarn: 'yarn add @qwik-ui/headless',
-  pnpm: 'pnpm add @qwik-ui/headless',
+  npm: 'npm i -D @qwik-ui/headless',
+  yarn: 'yarn add -D @qwik-ui/headless',
+  pnpm: 'pnpm i -D @qwik-ui/headless',
 };
 
 export const qwikCityPackages = {