Updated README.md to add a step regarding .env

[ShadowFox88]

Description

This PR simply adds a section to the README.md instructions on setting up the application with docker. It lets users know that there is a .env.example to copy to .env.

On an unrelated note, for the redis.conf, there is no mention of a password within it, yet it says to edit the password for added security, should this not exist there?

Checklist

• If code changes were made then they have been tested.
  • I have updated the documentation to reflect the changes.
  • I have updated the changelog with a quick recap of my changes.
• This PR fixes an issue.
• This PR adds something new (e.g. new method or parameters).
• This PR is a breaking change (e.g. methods or parameters removed/renamed)
• This PR is not a code change (e.g. documentation, README, ...)
• I have read and agree to the Developer Certificate of Origin for this contribution

[AbstractUmbra]

Hey, thanks for the PR and time spent on this.

I'm a bit hesitant to merge this, due to waiting on #60 which would ultimately supercede this. I'll have a talk with @LostLuma about timescales and get back to you.