Publish releases from GHA

Automatically publish releases to NPM and Docker Hub from GHA. Only
performs a release, when:

- all tests pass
- a new git tag is pushed (expected format "v1.0.0")
- git tag matches the version in package.json

The gating of releases happens in the 'check-release' job, which all
future release-* jobs depend on. This is where any final linting or
sanity checking can be done.

.github/workflows/push.yml

@@ -31,3 +31,74 @@ jobs:
         run: |
           export FORCE_COLOR=1
           ./dcmon --static-once dcmon-test ./examples/checks.yaml
+
+  # Decide if a release is necessary, do any release linting/checks
+  check-release:
+    needs: [ compose-tests ]
+    name: Check Release
+    runs-on: ubuntu-latest
+    if: startsWith(github.ref, 'refs/tags/v') && contains(github.ref, '.')
+    outputs:
+      RELEASE_VERSION: ${{ steps.get-version.outputs.RELEASE_VERSION }}
+    steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v4
+        with: { submodules: 'recursive', fetch-depth: 0 }
+
+      - id: get-version
+        name: Get release version
+        run: |
+          echo "RELEASE_VERSION=$(jq -r .version package.json)" | tee "$GITHUB_ENV" | tee "$GITHUB_OUTPUT"
+
+      - name: Check git tag matches release version
+        run: |
+          [ "refs/tags/v${RELEASE_VERSION}" == "${{ github.ref }}" ]
+
+  release-npm:
+    needs: [ check-release ]
+    name: Release NPM
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v4
+        with: { submodules: 'recursive', fetch-depth: 0 }
+
+      # Setup .npmrc file to publish to npm
+      - uses: actions/setup-node@v4
+        with:
+          node-version: '20.x'
+          registry-url: 'https://registry.npmjs.org'
+          scope: ''
+
+      - run: npm publish
+        env:
+          NODE_AUTH_TOKEN: ${{ secrets.NPM_TOKEN }}
+
+  release-docker-hub:
+    needs: [ check-release ]
+    name: Release Docker Hub
+    runs-on: ubuntu-latest
+    env:
+      RELEASE_VERSION: ${{ needs.check-release.outputs.RELEASE_VERSION }}
+    steps:
+      - name: Checkout Repository
+        uses: actions/checkout@v4
+        with: { submodules: 'recursive', fetch-depth: 0 }
+
+      - name: Login to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKERHUB_USERNAME }}
+          password: ${{ secrets.DOCKERHUB_TOKEN }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          push: true
+          tags: lonocloud/dcmon:${{ env.RELEASE_VERSION }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v6
+        with:
+          push: true
+          tags: lonocloud/dcmon:latest