fix(nix): Update flake.nix to configure Shell Plugins as functions vs. aliases

[mrjones2014]

Overview

Users of the Nix Flake will now have Shell Plugins wired up as shell functions instead of shell aliases. This results in a better tab completion experience.

Type of change

• [ ] Created a new plugin
• [ ] Improved an existing plugin
• [ ] Fixed a bug in an existing plugin
• [x] Improved contributor utilities or experience

Related Issue(s)

• Relates: #433 (Resolves for Nix Flake users but not others)

How To Test

1. However you consume the flake (e.g. as an input to your own flake) update the URL to git+file:///path/to/local/shell-plugins (replacing the file path as appropriate for your own system)˜
2. Rebuild your Nix configuration
3. Restart your shell
4. Check that Shell Plugins still work

Changelog

Update Nix Flake to configure Shell Plugins as shell functions instead of aliases for better tab completion.

[mrjones2014]

@edif2008 can we get this one approved and merged as well?