feat: add workflow for building docker image

Signed-off-by: Mark Sagi-Kazar <mark.sagikazar@gmail.com>

.github/workflows/.editorconfig

@@ -0,0 +1,2 @@
+[*.yml]
+indent_size = 2

.github/workflows/docker.yml

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+name: Docker
+
+on:
+  schedule:
+    - cron: '0 10 * * *' # everyday at 10am
+  push:
+    branches:
+      - master
+    tags:
+      - v*
+  pull_request:
+
+jobs:
+  build:
+    name: Build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v2
+
+      - name: Gather image information
+        id: info
+        run: |
+          DOCKER_IMAGE=ghcr.io/drakkan/sftpgo
+          VERSION=noop
+          if [ "${{ github.event_name }}" = "schedule" ]; then
+            VERSION=nightly
+          elif [[ $GITHUB_REF == refs/tags/* ]]; then
+            VERSION=${GITHUB_REF#refs/tags/}
+          elif [[ $GITHUB_REF == refs/heads/* ]]; then
+            VERSION=$(echo ${GITHUB_REF#refs/heads/} | sed -r 's#/+#-#g')
+            if [ "${{ github.event.repository.default_branch }}" = "$VERSION" ]; then
+              VERSION=edge
+            fi
+          elif [[ $GITHUB_REF == refs/pull/* ]]; then
+            VERSION=pr-${{ github.event.number }}
+          fi
+          TAGS="${DOCKER_IMAGE}:${VERSION}"
+          if [[ $GITHUB_REF == refs/tags/* ]]; then
+            TAGS="$TAGS,${DOCKER_IMAGE}:latest"
+          fi
+          echo ::set-output name=version::${VERSION}
+          echo ::set-output name=tags::${TAGS}
+          echo ::set-output name=created::$(date -u +'%Y-%m-%dT%H:%M:%SZ')
+
+      - name: Set up QEMU
+        uses: docker/setup-qemu-action@v1
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@v1
+
+#      - name: Login to GitHub Container Registry
+#        uses: docker/login-action@v1
+#        with:
+#          registry: ghcr.io
+#          username: ${{ github.repository_owner }}
+#          password: ${{ secrets.CR_PAT }}
+
+      - name: Build and push
+        uses: docker/build-push-action@v2
+        with:
+          # push: ${{ github.event_name != 'pull_request' }}
+          push: false
+          tags: ${{ steps.info.outputs.tags }}
+          labels: |
+            org.opencontainers.image.title=${{ github.event.repository.name }}
+            org.opencontainers.image.description=${{ github.event.repository.description }}
+            org.opencontainers.image.url=${{ github.event.repository.html_url }}
+            org.opencontainers.image.source=${{ github.event.repository.clone_url }}
+            org.opencontainers.image.version=${{ steps.info.outputs.version }}
+            org.opencontainers.image.created=${{ steps.info.outputs.created }}
+            org.opencontainers.image.revision=${{ github.sha }}
+            org.opencontainers.image.licenses=${{ github.event.repository.license.spdx_id }}