Add tests for NvChad via plenary #1727

Adding a test suite could ease testing suggested contributions (and an excuse to learn more lua).

Given plenary is already included in NvChad and has a test_harness module, that's probably the easiest option. There are examples in the plenary repository (see TESTS_README.md) and this blog post. The post links to an example lua nvim plugin template with example tests. Assuming that works, it should be pretty straightforward to add automation to GitHub Actions for pull requests.

For completeness (though probably too tricky, at least initially): I'm unaware of a straightforward option to automate testing examples in Docusaurus but perhaps using jest with a shell-script could be part of the build? It would probably need filtering, but codedown is a command line javascript tool to extract code sections from markdown that can then be piped to a scripting language like lua to run. I got the idea from mktestdocs: a customizable plugin for testing code in mkdocs, another documentation library popular for python packages.