run daily

.github/workflows/docker.yml

@@ -6,6 +6,8 @@ on:
       - master
   release:
     types: [published]
+  schedule:
+    - cron: '0 7 * * *'
 
 jobs:
   images:
@@ -16,7 +18,7 @@ jobs:
         uses: actions/checkout@v2.3.4
 
       - name: Set tag to latest
-        if: github.event_name == 'push' && github.ref == 'refs/heads/master'
+        if: (github.event_name == 'push' && github.ref == 'refs/heads/master') || github.event_name == 'schedule'
         run: |
           echo "DOCKER_TAG=latest" >> $GITHUB_ENV