feature: description attribute in plugin table

[onexbash]

Did you check the docs?

• I have read all the lazy.nvim docs

Is your feature request related to a problem? Please describe.

Hi, it would be cool to have a description attribute that can be added to the plugin specs.
This could also help to integrate which-key easier and give plugin devs the possibility to use this attribute.

Describe the solution you'd like

Additional "Description" attribute in Plugin Spec 'Source'

Describe alternatives you've considered

creating a custom lua function that exposes a global description variable per plugin (this solution was horrible)

Additional context

No response