Add GitHub Actions Docker build workflow

.github/workflows/docker.yml

@@ -0,0 +1,27 @@
+name: Build and push Docker image
+
+on:
+  push:
+    branches: [OAuth_Delegated_Token]
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+    steps:
+      - uses: actions/checkout@v4
+      - uses: docker/login-action@v3
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+      - uses: docker/setup-buildx-action@v3
+      - uses: docker/build-push-action@v6
+        with:
+          context: .
+          push: true
+          tags: ghcr.io/system-end/auth:latest
+          cache-from: type=gha
+          cache-to: type=gha,mode=max