vercel preview workflow

.github/workflows/preview.yml

@@ -0,0 +1,28 @@
+on:
+  pull_request:
+    branches: ['main']
+
+jobs:
+  foo:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/setup-node@v4
+      - uses: actions/checkout@v4
+      - run: |
+          npx -y vercel deploy --target=preview \
+            --build-env MDX=docs \
+            --build-env NEXT_PUBLIC_LIBNAME="Poimandres" \
+            --build-env NEXT_PUBLIC_LIBNAME_SHORT="pmndrs" \
+            --build-env BASE_PATH= \
+            --build-env DIST_DIR= \
+            --build-env OUTPUT=export \
+            --build-env HOME_REDIRECT=/introduction \
+            --build-env MDX_BASEURL="https://github.com/${{ github.repository }}/raw/${{ github.ref_name }}/docs" \
+            --build-env EDIT_BASEURL="https://github.com/${{ github.repository }}/edit/${{ github.ref_name }}/docs" \
+            --build-env NEXT_PUBLIC_URL="$VERCEL_PROJECT_PRODUCTION_URL" \
+            --build-env ICON="🖨️" \
+            --build-env LOGO=
+        env:
+          VERCEL_ORG_ID: ${{ secrets.VERCEL_ORG_ID }}
+          VERCEL_PROJECT_ID: ${{ secrets.VERCEL_PROJECT_ID }}
+          VERCEL_TOKEN: ${{ secrets.VERCEL_TOKEN }}

docs/introduction.mdx

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+---
+title: foo
+description: bar
+---
+
+This is pmndrs/docs documentation 🙃.
+
+# headin 1
+
+asdfasdf
+
+## sadf
+
+aooijoafdsi