Build an up'to'date container every week

Author: MattBlack85

.github/workflows/buildx.yml

@@ -5,6 +5,8 @@ on:
   push:
     branches: [ "main" ]
     tags: [ "v*", "release-*" ]
+  schedule:
+    - cron: '0 0 * * 0' # Every sunday at midnight
 
 permissions:
   contents: read