Add workflow to build app

.github/workflows/build.yml

@@ -0,0 +1,41 @@
+name: Build
+
+on:
+  push:
+    branches:
+      - main
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    env:
+      CONTAINER_REGISTRY: ghcr.io
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Build app
+        run: |
+          cd app
+          yarn install --immutable
+          yarn tsc
+          yarn build:backend --config ../../app-config.yaml --config ../../app-config.production.yaml
+
+      - name: Get Docker image tag
+        id: image_tags
+        run: |
+          echo "tag=$CONTAINER_REGISTRY/$(echo $GITHUB_REPOSITORY | tr '[:upper:]' '[:lower:]'):$GITHUB_SHA" >> $GITHUB_OUTPUT
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.CONTAINER_REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Docker build
+        run: |
+          cd app && docker build . --tag
+          docker push $TAG
+        env:
+          TAG: ${{ steps.image_tags.outputs.tag }}