fix: use vim.iter(...):flatten():totable()

[paulbrittain]

• fixes: 'Warning: vim.tbl_flatten is deprecated, use vim.iter(…):flatten():totable() instead.'
• replaces usage of vim.tbl_flatten() while keeping backward compatibility for < v0.10.0.

fixes issue: #414

[Copilot]

Pull Request Overview

This PR addresses the deprecation warning by replacing the usage of vim.tbl_flatten() with vim.iter(...):flatten():totable() for Neovim 0.10+ support while retaining backward compatibility for earlier versions.

• Replaces the direct use of vim.tbl_flatten() with a conditional that employs the new vim.iter(...):flatten():totable() syntax when available.
• Maintains support for older Neovim versions by falling back to vim.tbl_flatten().

[jamestrew]

Pull Request Overview

This PR addresses the deprecation warning by replacing the usage of vim.tbl_flatten() with vim.iter(...):flatten():totable() for Neovim 0.10+ support while retaining backward compatibility for earlier versions.

• Replaces the direct use of vim.tbl_flatten() with a conditional that employs the new vim.iter(...):flatten():totable() syntax when available.
• Maintains support for older Neovim versions by falling back to vim.tbl_flatten().

First time using this. Was just curious.

Thanks