Adding GHA for automatic image build and push (#1615)

* Adding latest image tag

* Update manifests with latest image tag

* Add github actions for image build/push

.github/workflows/publish-images.yaml

@@ -0,0 +1,34 @@
+name: Publish Training Images
+
+on:
+  push:
+    branches:
+      - master
+
+env:
+  DOCKERHUB_USERNAME: ${{ secrets.DOCKERHUB_USERNAME }}
+  DOCKERHUB_TOKEN: ${{ secrets.DOCKERHUB_TOKEN }}
+
+jobs:
+  trial:
+    name: Publish Image
+    # Trigger workflow only for kubeflow/training-operator repository.
+    if: github.repository == 'kubeflow/training-operator'
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Publish Docker Images ${{ matrix.name }}
+        uses: ./.github/workflows/template-publish-image
+        with:
+          image: docker.io/kubeflow/${{ matrix.name }}
+          dockerfile: ${{ matrix.dockerfile }}
+
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - name: training-operator
+            dockerfile: build/images/training-operator/Dockerfile
+          # Add example images in the future

.github/workflows/template-publish-image/action.yaml

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+# Template run for publishing images.
+
+inputs:
+  image:
+    required: true
+    type: string
+  dockerfile:
+    required: true
+    type: string
+
+runs:
+  using: composite
+  steps:
+    - name: Set Up Docker Buildx
+      uses: docker/setup-buildx-action@v1
+
+    - name: Docker Login
+      uses: docker/login-action@v1
+      with:
+        username: ${{ env.DOCKERHUB_USERNAME }}
+        password: ${{ env.DOCKERHUB_TOKEN }}
+
+    - name: Add Docker Tags
+      id: meta
+      uses: docker/metadata-action@v3
+      with:
+        images: ${{ inputs.image }}
+        tags: |
+          type=raw,latest
+          type=sha,prefix=v1-
+
+    - name: Build and Push
+      uses: docker/build-push-action@v2
+      with:
+        context: .
+        file: ${{ inputs.dockerfile }}
+        push: true
+        tags: ${{ steps.meta.outputs.tags }}
+        cache-from: type=gha
+        cache-to: type=gha,mode=max