Add example for login to Fly registry

README.md

@@ -495,6 +495,31 @@ jobs:
           password: ${{ secrets.DIGITALOCEAN_ACCESS_TOKEN }}
 ```
 
+### Fly.io
+
+Use an [access token](https://fly.io/docs/security/tokens/) to authenticate to the
+container registry.
+
+```yaml
+name: ci
+
+on:
+  push:
+    branches: main
+
+jobs:
+  login:
+    runs-on: ubuntu-latest
+    steps:
+      -
+        name: Login to Fly.io Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: registry.fly.io
+          username: x
+          password: ${{ secrets.FLY_API_TOKEN }}
+```
+
 ## Customizing
 
 ### inputs