Support for comprehensive email templating

[niveathika]

Description:
$subject

We need to generate email templates in many applications we develop.
As of now, we are using regEx and a combination of other workarounds.

We request to have support for the "mustache" templating library, so that we can generate dynamic email content easily.
Ref: https://mustache.github.io/

[niveathika]

A sample implementation https://github.com/MohamedSabthar/mustache