fix: respect telescope's `path_display`

[delphinus]

fix #47

Now path_display can be specified by these priorities.

1. Option specified with the command or Lua code.
   • :Telescope frecency path_display={"absolute"}.
   • or :lua require("telescope").extensions.frecency.frecency { path_display = { "absolute" } }.
2. opts.extensions.frecency.path_display in setup.

3. opts.defaults.path_display in setup.

    require("telescope").setup {
      defaults = {
        -- This has the 3rd precedence.
        path_display = { "absolute" },
      },
      extensions = {
        frecency = {
          -- This has the 2nd precedence.
          path_display = { "shorten" },
        },
      },
    }