ci: add workflow to test action

Signed-off-by: Hidde Beydals <hidde@hhh.computer>

.github/workflows/action.yaml

@@ -0,0 +1,29 @@
+name: test-gh-action
+
+on:
+  pull_request:
+    paths:
+      - 'action/**'
+  push:
+    paths:
+      - 'action/**'
+    branches:
+      - 'main'
+      - 'release/**'
+
+permissions: read-all
+
+jobs:
+  actions:
+    strategy:
+      fail-fast: false
+      matrix:
+        version: [ubuntu-latest, macos-latest, windows-latest]
+
+    runs-on: ${{ matrix.version }}
+    name: action on ${{ matrix.version }}
+    steps:
+      - name: Checkout
+        uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
+      - name: Setup flux
+        uses: ./action