Add github workflow to test the action

.github/workflows/test.yml

@@ -0,0 +1,20 @@
+name: Test action
+
+on:
+  pull_request:
+    branches: [master]
+
+jobs:
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v6
+
+      - name: Send plain message
+        uses: ./
+        with:
+          server: ${{ secrets.ROCKETCHAT_SERVER }}
+          user: ${{ secrets.ROCKETCHAT_USER }}
+          password: ${{ secrets.ROCKETCHAT_PASSWORD }}
+          channel: "#test-notifications-akiel"
+          message: "Test plain message from ${{ github.repository }}@${{ github.sha }}"