feat: add optional buf_id param to wildcard

[AgatZan]

Inspired by spooky.nvim

[cvigilv]

This can be easily done adding that wildcard to your config as follows:

reauire("esqueleto").setup({
  -- Your config...
  wildcards = {
    lookup = {
      ["bufid"] = function() vim.api.nvim_get_current_buf() end,
    },
  },
})

Let me know if this works for your needs, thanks for the issue.