Add GHA workflows.

.github/workflows/build-plot-navigator.yaml

@@ -0,0 +1,53 @@
+name: plot-navigator
+
+on:
+  push:
+    tags:
+      - "*"
+
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+
+    if: >
+      startsWith(github.ref, 'refs/tags/')
+
+    steps:
+
+      - name: Get tag name
+        run: echo "IMG_TAG=${GITHUB_REF#refs/*/}" >> $GITHUB_ENV
+
+      -
+        name: Set up QEMU
+        uses: docker/setup-qemu-action@v3
+      -
+        name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      -
+        name: Cache Docker layers
+        uses: actions/cache@v4
+        with:
+          path: /tmp/.buildx-cache
+          key: ${{ runner.os }}-buildx-${{ github.sha }}
+          restore-keys: |
+            ${{ runner.os }}-buildx-
+
+      -
+        name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.repository_owner }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      -
+        name: Build and push
+        id: docker_build
+        uses: docker/build-push-action@v5
+        with:
+          context: src
+          push: true
+          tags: ghcr.io/lsst-dm/plot-navigator:${{ env.IMG_TAG }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+

.github/workflows/rebase_checker.yaml

@@ -0,0 +1,8 @@
+---
+name: Check that 'main' is not merged into the development branch
+
+on: pull_request
+
+jobs:
+  call-workflow:
+    uses: lsst/rubin_workflows/.github/workflows/rebase_checker.yaml@main