2025-07-12: Add render-markdown plugin and improve copilot UI integration

[john-mutuma]

What does this PR do?

This PR enhances the NairoVIM configuration by adding markdown rendering capabilities and improving the user interface integration with GitHub Copilot. The changes include adding a new render-markdown plugin for better markdown display and updating the lualine configuration to hide the statusline in copilot interface windows for a cleaner user experience.

• Add render-markdown.nvim plugin for enhanced markdown display in-editor
• Add mini.nvim dependency to support render-markdown functionality
• Update lualine configuration to hide statusline in copilot-chat and copilot-overlay windows
• Improve code formatting in lualine configuration file

Why is it needed?

• Enhanced markdown rendering improves readability of documentation, README files, and markdown content within the editor
• Hiding the statusline in copilot interface windows provides a cleaner, more focused UI when using AI assistance features
• The mini.nvim dependency provides essential utilities and icons for the render-markdown plugin to function properly

How have the changes been tested?

• Verified that render-markdown plugin loads correctly with treesitter and mini.nvim dependencies
• Tested lualine behavior with copilot-chat and copilot-overlay filetypes to ensure statusline is properly hidden
• Confirmed that existing lualine functionality remains intact for other file types
• Validated that markdown files now render with improved visual formatting

Screenshots (if applicable)

N/A - UI improvements are visible when using copilot features and viewing markdown files in the editor

Checklist

• Plugin dependencies are correctly specified in render-markdown configuration
• Lualine blank filetypes updated to include copilot interface windows
• Code formatting improvements applied to lualine configuration
• No breaking changes to existing lualine functionality
• New plugins added to lazy-lock.json for version tracking
• Plugin configuration follows NairoVIM project structure conventions