ci: add test deploy on fly with gh actions

.github/workflows/main.yml

@@ -0,0 +1,14 @@
+name: Fly Deploy
+on: [push]
+env:
+  FLY_API_TOKEN: ${{ secrets.FLY_API_TOKEN }}
+jobs:
+  deploy:
+      name: Deploy app
+      runs-on: ubuntu-latest
+      steps:
+        - uses: actions/checkout@v2
+        - uses: superfly/flyctl-actions@1.1
+          with:
+            args: "deploy"
+