Feat: Allow overriding channel config via .env file

[Asartea]

Because

• #582

This PR

• Allows channel ID's to be overridden via .env
• Modifies .env.sample to include a note on this functionality

Issue

Closes #582

Additional Information

Pull Request Requirements

• [x] I have thoroughly read and understand The Odin Project Contributing Guide
• [x] The title of this PR follows the location of change: brief description of change format, e.g. Callbacks command: Update verbiage
• [x] The Because section summarizes the reason for this PR
• [x] The This PR section has a bullet point list describing the changes in this PR
• [x] If this PR addresses an open issue, it is linked in the Issue section
• [x] If applicable, I have ensured all tests related to any command files included in this PR pass, and/or all snapshots are up to date