ci: add release workflow to publish the crate

.github/workflows/release.yml

@@ -0,0 +1,22 @@
+name: Publish to crates.io
+
+on:
+  release:
+    types: [created]
+
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+    - name: Checkout repository
+      uses: actions/checkout@v2
+
+    - name: Set up Rust
+      uses: actions/setup-rust@v1
+      with:
+        rust-version: stable
+
+    - name: Publish to Crates.io
+      env:
+        CARGO_REGISTRY_TOKEN: ${{ secrets.CARGO_REGISTRY_TOKEN }}
+      run: cargo publish