Bring taxon and taxonomy factories from spree_core

spec/factories/taxon_factory.rb

@@ -0,0 +1,7 @@
+FactoryBot.define do
+  factory :taxon, class: Spree::Taxon do
+    name 'Ruby on Rails'
+    taxonomy
+    parent_id nil
+  end
+end

spec/factories/taxonomy_factory.rb

@@ -0,0 +1,5 @@
+FactoryBot.define do
+  factory :taxonomy, class: Spree::Taxonomy do
+    name 'Brand'
+  end
+end