add test workflow

.forgejo/workflows/action.yml

@@ -0,0 +1,16 @@
+name: Test action
+
+on:
+  workflow_dispatch:
+  push:
+    branches:
+      - main
+
+jobs:
+  hello:
+    name: Print hello world
+    runs-on: ubuntu-latest
+    steps:
+      - name: Echo
+        run: |
+          echo "Hello, world!"