build: Run cargo-audit from a GitHub action

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

.github/workflows/audit.yaml

@@ -0,0 +1,15 @@
+name: Cloud Hypervisor Dependency Audit
+on:
+  pull_request:
+    paths: 
+      - '**/Cargo.toml'
+      - '**/Cargo.lock'
+jobs:
+  security_audit:
+    name: Audit
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1
+      - uses: actions-rs/audit-check@v1
+        with:
+          token: ${{ secrets.GITHUB_TOKEN }}