chore(workflows): switch to pnpm

Author: wingkwong

.github/workflows/deploy.yml

@@ -15,13 +15,12 @@ jobs:
       - uses: actions/checkout@v4
       - uses: actions/setup-node@v4
         with:
-          node-version: 18
-          cache: npm
+          cache: 'pnpm'
 
       - name: Install dependencies
-        run: npm ci
+        run: pnpm install
       - name: Build website
-        run: npm run build
+        run: pnpm run build
 
       # Popular action to deploy to GitHub Pages:
       # Docs: https://github.com/peaceiris/actions-gh-pages#%EF%B8%8F-docusaurus