[NEW] Twilio MMS support for LiveChat integration (#7964)

* Added ability for MMS messaging to push through attachments

* Fixed issues for codacy https://www.codacy.com/app/RocketChat/Rocket-Chat/pullRequest?prid=875706

* Fixed more codacy issues

* Changes concerning feedback from dev

* Switch to camelcase
* Changed hasMedia (removed)
* use map instead of for loop for populating attachments

* Save map return on message attachments