enable copilot to generate commit message based on related changes

[dryezl]

The function is enabled in vscode. However, I did not know how to implement it in vim.
I use vim-fugitive in vim to control git.

[dryezl]

I found that g:copilot_workspace_folders can allow for context to improve suggestion.
perhaps a vim function to send commit prompt ("create a commit message based on related change") and those related change to copilot.