Add release workflow.

.github/workflows/release.yml

@@ -0,0 +1,29 @@
+name: Publish package to crates
+
+on:
+  release:
+    types: [created]
+
+jobs:
+  publish:
+
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Setup Rust
+        uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          override: true
+
+      - name: Publish to crates.io
+        uses: katyo/publish-crates@v1
+        with:
+          registry-token: ${{ secrets.CARGO_TOKEN }}