Feature: TSV file generation

**Is your feature request related to a problem? Please describe.**
Model-builder plugin can automatically create .tsv file from folder structure, but there is no simple way to get this file.

**Describe the solution you'd like**
I would like a way to access the generated .tsv file, even before any learning has been commenced. I currently just go to the TEMP folder and find the latest .tsv file there, but this is a bothersome workaround.

**Describe alternatives you've considered**
A library function that could be called on a folder would be nice too.

**Additional context**
This is related to my question on marketplace:

https://marketplace.visualstudio.com/items?itemName=MLNET.07&ssr=false#qna

`I love the simple approach to loading image data, can we get a tool and also a function in code to allow us to get the .tsv file directly from folder? Currently I have to load the data, then go to %appdata%/Local/Temp and find the generated .tsv file if I want to use it.`

ファイル、テスト、エントリーポイントは指定されていません。まず model-builder plugin の TSV 生成パスを特定し、学習が始まる前に生成されたファイルを公開できる方法を確認してください。ユーザーが TEMP フォルダーを検索せずに直接アクセスできれば完了です。

索引モデルが issue の本文から書いたものです。