[FR] replace vim.fn.input with vim.ui.input

[jiz4oh]

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

no

Describe the solution you'd like

neovim v0.6 had provided a public api named vim.ui.input that lets user customize the input UI. could you considering replace all the vim.fn.input implementations with vim.ui.input, the default behavior is consistent with vim.fn.input so it doesn't break anything existing

Describe alternatives you've considered

Additional context

I'd like to open a PR if you agreed that