chore: make to fuzzy refine easily configurable

[Conni2461]

CC @clason

telescope.setup {
  -- defaults = { },
  pickers = {
    live_grep = {
      mappings = {
        i = { ["<c-f>"] = actions.to_fuzzy_refine },
      },
    },
  },
  -- extensions = { },
}

[SophisticaSean]

here's a lua config working example:

local actions = require('telescope.actions')
require('telescope').setup {
  -- defaults = { },
  pickers = {
    live_grep = {
      mappings = {
        i = { ["<c-f>"] = actions.to_fuzzy_refine },
      },
    },
  },
  -- extensions = { },
}

[bangedorrunt]

@Conni2461 got this error when set border = false

E5108: Error executing lua .../start/telescope.nvim/lua/telescope/actions/generate.lua:79: attempt to index field 'prompt_border' (a nil value)
stack traceback:
	.../start/telescope.nvim/lua/telescope/actions/generate.lua:79: in function 'refine'
	...cker/start/telescope.nvim/lua/telescope/actions/init.lua:1320: in function 'run_replace_or_original'
	...packer/start/telescope.nvim/lua/telescope/actions/mt.lua:65: in function 'key_func'
	...k/packer/start/telescope.nvim/lua/telescope/mappings.lua:341: in function 'execute_keymap'
	[string ":lua"]:1: in main chunk