added container build workflow

.github/workflows/container.yml

@@ -0,0 +1,25 @@
+name: Container
+on:
+  push:
+    branches:
+      - master
+    tags:
+      - "*"
+jobs:
+  docker:
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v2
+      - name: Get current tag
+        id: get_current_tag
+        run: echo ::set-output name=tag::${GITHUB_REF#refs/*/}
+      - uses: mr-smithers-excellent/docker-build-push@v5
+        name: Build & push Docker image
+        with:
+          registry: ghcr.io
+          username: ${{ secrets.GHCR_USER }}
+          password: ${{ secrets.GHCR_TOKEN }}
+          dockerfile: Dockerfile
+          image: k4yt3x/video2x
+          tags: latest, ${{ steps.get_current_tag.outputs.tag }}