Inline Solidus Frontend

Merge frontend/Rakefile into Rakefile.

Rakefile

@@ -1,5 +1,25 @@
 # frozen_string_literal: true
 
+require 'rubygems'
+require 'rake'
+require 'rake/testtask'
+require 'rspec/core/rake_task'
+require 'spree/testing_support/dummy_app/rake_tasks'
+
+RSpec::Core::RakeTask.new
+task default: :spec
+
+DummyApp::RakeTasks.new(
+  gem_root: File.expand_path(__dir__),
+  lib_name: 'solidus_frontend'
+)
+
+task test_app: 'db:reset'
+
+#-------------------------------------------------------------------------------
+
+# frozen_string_literal: true
+
 require 'bundler'
 
 task default: :spec