feat(gha): generate API doc

Introduces a new GitHub Actions workflow `doc.yml` which generates API
documentation and uploads it to GitHub Pages.

.github/workflows/doc.yml

@@ -0,0 +1,38 @@
+name: Generate API doc
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  doc:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+      - name: Generate API doc
+        run: cargo doc --lib --no-deps --all-features
+      - name: Upload API doc as artifact
+        id: artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: target/doc
+
+  deploy:
+    needs: doc
+
+    permissions:
+      pages: write
+      id-token: write
+
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+
+    runs-on: ubuntu-latest
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4