feat(port): add zellij port

[arrrgi]

Description

This PR: Adds support for Zellij, a terminal workspace, aka "multiplexer" written in Rust.

Assets

Checklist

• PR description included
• I've read the documents
• I've created or commented in an issue related to this port asking to work on it
• I know I shouldn't change any files in the packages folder manually
• I've added this port at the end of the related category list in the main README
• I've attached an image to the icon of the app that this port is related to
• I've attached a screenshot with a good zoom in fullscreen showing this port in action

PR Submitter Notes

1. Regarding CLI and Syntax highlighter ports #244 - I have not added this to the Aura Theme README as it deserves it's own section
2. I also haven't included the preview in the main README as these are stored in your 'assets' repo