Add pre_checkout_query to PAYLOAD_TYPES (#238)

* Update Bot API version from 7.5 to 7.7
- Add new method: sendPaidMedia

* Add pre_checkout_query to PAYLOAD_TYPES

- Added pre_checkout_query to updates_controller.rb
- Updated tests in updates_controller_spec.rb
- Updated tests in typed_update_spec.rb
- Updated CHANGELOG.md for Bot API 7.7 and pre_checkout_query

spec/telegram/bot/updates_controller/typed_update_spec.rb

@@ -28,6 +28,7 @@ RSpec.describe Telegram::Bot::UpdatesController::TypedUpdate do
       message_reaction_count
       chat_boost
       removed_chat_boost
+      pre_checkout_query
     ]).
       map { |x| [x, Telegram::Bot::Types.const_get(x.camelize)] }.to_h.
       merge(