ci: switched image push to use Gitub Actions

Author: itzg

.github/workflows/main.yml

@@ -1,6 +1,6 @@
 # This is a basic workflow to help you get started with Actions
 
-name: Build non-multiarch branches/tags
+name: Build and publish non-multiarch branches/tags
 
 on:
   push:
@@ -36,4 +36,4 @@ jobs:
         tag_with_sha: true
         cache_froms: itzg/minecraft-server:latest
         add_git_labels: true
-        push: false
+        push: true