INIT(docusaurus): setup GitHub Actions CI/CD

- Add Docusaurus source in docusaurus/ folder
- Create multi-stage Dockerfile (Node.js build + Nginx)
- Configure GitHub Actions for CI and Docker build
- Add nginx config for SPA routing

.github/workflows/build.yml

@@ -0,0 +1,76 @@
+name: Build Docker Image
+
+on:
+  push:
+    branches: [main]
+    tags:
+      - 'v*'
+  workflow_dispatch:
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-24.04-arm
+    permissions:
+      contents: read
+      packages: write
+
+    outputs:
+      image-tag: ${{ steps.meta.outputs.tags }}
+      image-digest: ${{ steps.build.outputs.digest }}
+
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v3
+
+      - name: Log in to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.CR_PAT }}
+
+      - name: Lowercase repository name
+        id: lowercase
+        run: |
+          echo "repo=$(echo ${{ github.repository }} | tr '[:upper:]' '[:lower:]')" >> $GITHUB_OUTPUT
+
+      - name: Extract metadata (tags, labels)
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ steps.lowercase.outputs.repo }}
+          tags: |
+            type=sha,prefix=sha-,format=long
+            type=raw,value=latest,enable={{is_default_branch}}
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+
+      - name: Build and push Docker image
+        id: build
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: ./Dockerfile
+          build-contexts: |
+            docusaurus=./docusaurus
+            nginx=./nginx
+          push: true
+          platforms: linux/arm64
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
+      - name: Display image information
+        run: |
+          echo "Image built and pushed successfully!"
+          echo "Image tags:"
+          echo "${{ steps.meta.outputs.tags }}"
+          echo "Digest: ${{ steps.build.outputs.digest }}"