Add .env file support for backend

[LucientZ]

Overview

Generally, it's a good idea for the developer to be able to set environment variables in a .env file when running an application locally. This is especially true when working on different projects that might have the same names for environment variables. The backend should be able to load said file if it exists into it's own environment on runtime

Ideas

• The .env file should be loaded from the /backend directory since the frontend also has a .env file it reads from.