add a github action workflow to build operator

.github/workflows/publish-operator.yml

@@ -0,0 +1,27 @@
+name: Publish Dev Operator
+
+on:
+  push:
+    tags:
+      - 'v*.*.*'
+jobs:
+  publish:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v2
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+      - name: Build and publish k8s-operator image
+        env:
+          REPO: ghcr.io/${{ github.repository_owner }}/tailscale
+          TAGS: ${{ github.ref_name }}
+          PLATFORM: linux/amd64
+        run: |
+          echo "Building and publishing to ${REPO} with tags ${TAGS}"
+          export REPO
+          export TAGS
+          export PLATFORM
+          make publishdevoperator