github: add Kani to Github CI

.github/workflows/kani.yml

@@ -0,0 +1,14 @@
+# From https://model-checking.github.io/kani/install-github-ci.html
+name: Kani CI
+on:
+  pull_request:
+  push:
+jobs:
+  run-kani:
+    runs-on: ubuntu-20.04
+    steps:
+      - name: 'Checkout your code.'
+        uses: actions/checkout@v3
+
+      - name: 'Run Kani on your code.'
+        uses: model-checking/kani-github-action@v0.15