Reusable button
Implemented the reusable button.
- Including a class named button_type.dart with an enum(ButtonType) with different button options with a factory named ButtonTypeExtension.
- ButtonTypeExtension generates button specifications for each enum type.
- Those specifications are stored in ButtonConfigurations class inside button_configurations.dart file.
- Finaly, in the reusable_button.dart file inside the ReusableButton class all previously set up configurations are called to the initializer and used on the Widget build's definitions.