[Suggestion]: Ability to specify searching directories or files in the interactive picker

### Which fff frontend(s)?

Neovim plugin (fff.nvim)

### What problem are you trying to solve?

I see it's possible to specify whether to search directories or files programmatically but I don't see this option for the interactive picker. What I'm trying to build is the following (where I use fzf-lua):

```lua
vim.keymap.set('n', '',
function()
plugin.fzf_exec("fd --follow --type directory --hidden --max-depth 4 . $HOME", {
prompt = "Goto -> ",
actions = {
['default'] = function(selected)
vim.cmd("cd " .. selected[1])
end
},
})
end,
{desc = 'Change directory (home)'})
```

### Proposed solution

_No response_

Start by tracing fff.nvim's interactive picker and comparing it with the existing programmatic option to search directories or files. Done means the interactive picker can select whether to search directories or files, including the directory-navigation use case described with fzf-lua and fd.

Written by the indexing model from the issue text.