[Feature - Inline Audio Message] - Mini audio player added if message is audio.

[milos-dukic]

I created a PR for the issue #99 . If the message is audio, sound bar will appear, and will animate during the play time. The message is not auto-played, it has to be triggered by the user. Also the length of the message is displayed at the bottom of the message bubble. Preview:

Files afected:

• app/assets/stylesheets/soundbar.css - new animation effects
• app/helpers/messages/attachment_presentation.rb - new audio_preview_tag method added.
• app/javascript/controllers/sound_controller.js - existing controller updated

Cheers!