Add workflow for cargo-audit

.github/workflows/audit.yml

@@ -0,0 +1,17 @@
+name: cargo-audit
+
+on:
+  push:
+    paths:
+      - "**/Cargo.toml"
+      - "**/Cargo.lock"
+  pull_request:
+
+jobs:
+  audit:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2.3.3
+      - uses: actions-rs/audit-check@v1.2.0
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}