[docs] add cooler 😎 screenshots 🖼️ of the UI

README.md

@@ -15,8 +15,7 @@ of it and is prepared to be able to accommodate several Time Banks in a single i
 for this account with three levels of privileges: superadmin, admin (only manages a bank)
 and members of a bank.
 
-![Users list](docs/images/usuarios.png)
-![Offers list](docs/images/ofertas.png)
+![Demo UI](docs/images/demo_ui.jpeg)
 
 TimeOverflow is divided into 2 large blocks:
 

spec/controllers/users_controller_spec.rb

@@ -441,8 +441,8 @@ RSpec.describe UsersController do
 
       let(:uploaded_file) do
         Rack::Test::UploadedFile.new(
-          Rails.root.join("docs/images/ofertas.png"),
-          "image/png"
+          Rails.root.join("docs/images/demo_ui.jpeg"),
+          "image/jpeg"
         )
       end