document better how to read xlsx files (and support multisheet xlsx files)

[behrica]

Maype point here:

https://techascent.github.io/tech.ml.dataset/tech.v3.libs.fastexcel.html

But in any case "pure tablecloth" will then only read xlsx files with one sheet.

tech.ml.dataset supports multi sheet , in this way, reading first sheet for example.

(ns xxxx
  (:require [tablecloth.api :as tc]
            [tech.v3.libs.fastexcel]))

(->
 (tech.v3.libs.fastexcel/input->workbook "my-file-with-mutiple-sheets.xlsx")
 first
 (tech.v3.dataset.io.spreadsheet/sheet->dataset {}))

[genmeblog]

Maybe we can add additional small namespace to cover this case? I think about adding two functions: workbook and sheet->dataset + an alias in deps.edn with required dependency. Is there anything more worth importing?

[behrica]

Maybe we want that "tablecloth" has excel and arrow import working out of the box.
But then it would need to declare depdendencies on it, which dataset avoided to do.

I think it is a "showstoper" for a beginner to not be able to load an excel file without additional dependencies. (same for arrow)