Signoz alert manager setup for SMTP

[BryanFauble]

Background documentation:

1. https://signoz.io/docs/alerts-management/notification-channel/email/

Problem:

1. For alert manager to send out email it needs authentication to an SMTP server to send out those emails.

Solution:

1. I set up the connection for alert-manager to use gmail for SMTP

Testing:

1. I verified with temporary credentials that I was able send out a test notification:
   

[BryanFauble]

Moved to #41