initial commit of Docker config(s) and workflow

.dockerignore

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+node_modules
+npm-debug.log
+.next

.github/workflows/docker.yml

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+name: Build and Push to Docker Hub
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  push_to_registry:
+    name: Push Docker image to Docker Hub
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out repo
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to Docker Hub
+        uses: docker/login-action@v3
+        with:
+          username: ${{ secrets.DOCKER_USERNAME }}
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: gregrickaby/viewer-for-reddit
+
+      - name: Build and push
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: ./Dockerfile
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}

Dockerfile

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+# Use the official Node.js 20 image.
+# https://hub.docker.com/_/node
+FROM node:20-alpine
+
+# Create and change to the app directory.
+WORKDIR /usr/src/app
+
+# Copy application dependency manifests to the container image.
+# A wildcard is used to ensure both package.json AND package-lock.json are copied.
+# Copying this separately prevents re-running npm install on every code change.
+COPY package*.json ./
+
+# Install production dependencies.
+RUN npm ci
+
+# Copy local code to the container image.
+COPY . .
+
+# Build the application for production.
+RUN npm run build
+
+# Run the web service on container startup.
+CMD [ "npm", "start" ]