[docs] Update documentation to include how to connect to each DB through `porter run`

[abelanger5]

Location

• [X] Documentation
• [ ] Browser
• [ ] CLI
• [ ] API

Motivation

It should be possible to connect to each database through porter run. Some databases may require a separate worker service that runs a client for that database.

Requirements

Document how to connect to each of the 3 databases through porter run:

• [ ] Postgres
• [ ] Redis
• [ ] MongoDB

Additional Details

Raw .md files will be uploaded to the /docs folder of the repo as soon as this issue is assigned. It will be editable from there so that your contributions will show up in the main repo.