Add pattern matching support for Telegram types

[smaximov]

This PR adds support for pattern-matching Telegram types.

Some silly example:

update = Telegram::Bot::Api::Update.new(payload)

include Telegram::Bot::Api::Types

case update
in Update(message: Message(text: text, from: User(id: telegram_id, is_bot: false)))
  bot.api.send_message(chat_id: telegram_id, text: text.reverse)
in Update(message: Message(text: text, from: User(id: telegram_id, is_bot: true)))
  bot.api.send_message(chat_id: telegram_id, text: 'No bots allowed!')
else
  # unsupported update type
end

[atipugin]

@smaximov looks good, thanks! Merged.