chore: add staging workflow

Author: Vilsol

.github/workflows/staging.yml

@@ -0,0 +1,47 @@
+name: staging
+
+on:
+  push:
+    branches:
+      - staging
+
+jobs:
+  image:
+    name: Image
+    runs-on: ubuntu-latest
+    steps:
+      - name: Check out code into the Go module directory
+        uses: actions/checkout@v2
+        with:
+          fetch-depth: 0
+
+      - name: Login to GitHub Container Registry
+        uses: docker/login-action@v1
+        with:
+          registry: ghcr.io
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata (tags, labels) for Docker
+        id: meta
+        uses: docker/metadata-action@v3
+        with:
+          images: ghcr.io/${{ github.repository }}
+          flavor: |
+            latest=false
+          tags: |
+            type=raw,value=staging
+
+      - name: Set up Docker Buildx
+        id: buildx
+        uses: docker/setup-buildx-action@v1
+        with:
+          buildkitd-flags: --debug
+
+      - name: Build and push Docker image
+        uses: docker/build-push-action@v2
+        with:
+          context: .
+          push: false
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}