Macro: Add attachment for side conversation macro

Feature Request Summary: 

Macro: Add attachment functionality in 'Side conversation via email' actions

Description/Use Cases: 

Agents need to manually add attachment on the same macros they are using. Adding attachment button would allow agent to use macro and send quick email to our stakeholder without having to attach same document.

Business impact of limitation or missing feature:

Add attachment only available on 'Comment/description' action. This could be extended to side conversation via email and also child ticket.