Ability to attach an image to budgets

Co-authored-by: decabeza <alberto@decabeza.es>

spec/system/admin/budgets_spec.rb

@@ -1,6 +1,14 @@
 require "rails_helper"
 
 describe "Admin budgets", :admin do
+  it_behaves_like "nested imageable",
+                  "budget",
+                  "new_admin_budgets_wizard_budget_path",
+                  {},
+                  "imageable_fill_new_valid_budget",
+                  "Continue to groups",
+                  "New participatory budget created successfully!"
+
   context "Load" do
     before { create(:budget, slug: "budget_slug") }