Add workflow for pushing loadtester image

Signed-off-by: Stefan Prodan <stefan.prodan@gmail.com>

.github/workflows/push-ld.yml

@@ -0,0 +1,43 @@
+name: push-ld
+on:
+  workflow_dispatch:
+
+jobs:
+  build-push:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - name: Prepare
+        id: prep
+        run: |
+          VERSION=$(grep 'VERSION' cmd/loadtester/main.go | head -1 | awk '{ print $4 }' | tr -d '"')
+          echo ::set-output name=BUILD_DATE::$(date -u +'%Y-%m-%dT%H:%M:%SZ')
+          echo ::set-output name=VERSION::${VERSION}
+      - name: Setup QEMU
+        uses: docker/setup-qemu-action@v1
+        with:
+          platforms: all
+      - name: Setup Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+        with:
+          buildkitd-flags: "--debug"
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v1
+        with:
+          registry: ghcr.io
+          username: fluxcdbot
+          password: ${{ secrets.GHCR_TOKEN }}
+      - name: Publish image
+        uses: docker/build-push-action@v2
+        with:
+          push: true
+          builder: ${{ steps.buildx.outputs.name }}
+          context: .
+          file: ./Dockerfile
+          platforms: linux/amd64
+          tags: |
+            ghcr.io/fluxcd/flagger-loadtester:${{ steps.prep.outputs.VERSION }}
+      - name: Check images
+        run: |
+          docker buildx imagetools inspect ghcr.io/fluxcd/flagger-loadtester:${{ steps.prep.outputs.VERSION }}