Format codebase using Elixir's autoformatter

[ne1ro]

Elixir has a built-in autoformatter that allow us to keep codebase in one consistent style. This should significantly improve reading and changing of code.

Notable changes:

• Codebase was formatted by Elixir's autoformatted
• .formatter.exs with initial configuration was created

[BlakeWilliams]

I debated with myself about this one for a minute because Elixir's formatter output isn't exactly easy on the eyes compared to something like prettier. That being said it's probably better to go with the flow here than fight against it.

Thanks for the contribution!