Extract builder from app

Building is different from running

lib/tasks/mrsk/builder.rake

@@ -0,0 +1,27 @@
+require_relative "setup"
+
+namespace :mrsk do
+  namespace :builder do
+    desc "Deliver a newly built app image to servers"
+    task deliver: %i[ push pull ]
+
+    desc "Build locally and push app image to registry"
+    task :push do
+      run_locally do 
+        begin
+          info "Building multi-architecture images may take a while (run with VERBOSE=1 for progress logging)"
+          execute *MRSK.builder.push
+        rescue SSHKit::Command::Failed => e
+          error "Missing compatible buildx builder, so creating a new one first"
+          execute *MRSK.builder.create
+          execute *MRSK.builder.push
+        end
+      end unless ENV["VERSION"]
+    end
+
+    desc "Pull app image from the registry onto servers"
+    task :pull do
+      on(MRSK.config.hosts) { execute *MRSK.builder.pull }
+    end
+  end
+end