Docs: Update AWS Self Hosting Guide

[wh1337]

I would like to update the docs for AWS self-hosting with the following:

• Installing on a EC2 instance
• Connecting to AWS Document DB
• Connecting to AWS ElasticCache
• Reverse Proxy

If you can assign this task to me, I will write the docs up for your review. We are about to re-deploy Novu to our VPC and I plan to document the journey and would like to share it with the community.

[unicodeveloper]

Done @wh1337 !