Add action to push docker images

.github/workflows/release.yml

@@ -0,0 +1,22 @@
+name: Publish Docker
+on:
+  push:
+    branches:
+      - master
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@master
+    - name: Get release version
+      id: get_release_tag
+      run: echo ::set-env name=RELEASE_VERSION::$(echo $(date '+%Y%m%d'))
+    - name: Publish to Registry
+      uses: elgohr/Publish-Docker-Github-Action@master
+      with:
+        name: wiiuenv/wiiumodulesystem
+        username: ${{ secrets.DOCKER_USERNAME }}
+        password: ${{ secrets.DOCKER_PASSWORD }}
+        snapshot: true
+        cache: true
+        tags: "latest, ${{ env.RELEASE_VERSION }}"