Parse entities when sending request

[toniop99]

• [x] All tests pass
• [x] I have run npm run doc

Description

Is needed to stringify some options related with send arrays of messageEntities as specified in the doc of Telegram. Using same method as for replyMarkup with _fixReplyMarkup

There are three possible options fields wich need to be stringified. (entities, caption_entities and explanation_entities)

References

• Telegram Bot API - sendMessage (entities): https://core.telegram.org/bots/api#sendmessage
• Telegram Bot API - copyMessage (caption_entities): https://core.telegram.org/bots/api#copymessage
• Telegram Bot API - sendPoll (explanation_entities): https://core.telegram.org/bots/api#sendpoll