Add workflows to publish latest image automatically.

Signed-off-by: RainbowMango <qdurenhongcai@gmail.com>

.github/workflows/image.yml

@@ -0,0 +1,29 @@
+name: Image
+on:
+  push:
+    branches:
+      - master
+jobs:
+  publish-image:
+    name: publish images
+    # prevent job running from forked repository, otherwise
+    # 1. running on the forked repository would fail as missing necessary secret.
+    # 2. running on the forked repository would use unnecessary GitHub Action time.
+    if: ${{ github.repository == 'karmada-io/karmada' && github.ref == 'refs/heads/master' }}
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout code
+        uses: actions/checkout@v2
+      - name: install Go
+        uses: actions/setup-go@v2
+        with:
+          go-version: 1.14.x
+      - name: build images
+        env:
+          REGISTRY: ${{secrets.SWR_REGISTRY}}
+          REGISTRY_USER_NAME: ${{secrets.SWR_REGISTRY_USER_NAME}}
+          REGISTRY_PASSWORD: ${{secrets.SWR_REGISTRY_PASSWORD}}
+          REGISTRY_SERVER_ADDRESS: ${{secrets.SWR_REGISTRY_SERVER_ADDRESS}}
+          VERSION: latest
+
+        run: make upload-images