Add Actions job to publish to crates.io

Author: dcroote

.github/workflows/ci.yml

@@ -26,3 +26,18 @@ jobs:
           use-cross: true
           command: build
           args: --target ${{ matrix.target }}
+
+  cargo-publish:
+    name: Publish to crates.io
+    if: github.event_name == 'push' && startsWith(github.ref, 'refs/tags/')
+    runs-on: ubuntu-latest
+    needs: [build]
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions-rs/toolchain@v1
+        with:
+          toolchain: stable
+          profile: minimal
+          override: true
+      - name: Publish
+        run: cargo publish --token ${{ secrets.CRATES_IO_TOKEN }}