documentation: README completness, debug ocrd-tool.json

[tboenig]

Please debug your ocrd_tool.json file. I found an error:

<report valid="false">
  <error>[tools.ocrd-segment-evaluate] 'output_file_grp' is a required property</error>
</report>

You can find the ocrd-tool.json documentation: https://ocr-d.github.io/ocrd_tool

Please check your README file and complet them. An ideal README file look like:

# Name of application

## Introduction
...

## Installation
...

## Usage
...

## Testing
...

Thank you very much.

[bertsky]

This is an error of the validator in core, not of this repo. See OCR-D/core#295. Closing.

[tboenig]

For the error that's true, but look at the README file please and complete it. Thank you.