Issue #3319925 by komalparmar, Pracheth, abramm: Replace README.txt with README.md

-- SUMMARY --

##  SUMMARY 

The Extrafield Views Integration Module enables all Drupal core extra fields in

the system from type "display" as fields in views.

-- REQUIREMENTS --

## REQUIREMENTS 

Views

Entity

 -- INSTALLATION --

## INSTALLATION 

For installing the module, just download the source code and enable the module.

That's all.

-- CONFIGURATION --

## CONFIGURATION 

The module itself needs no configuration, because the extra fields that you

want to use need an render_class key and a class implements ExtrafieldRenderClassInterface.

Every module can use hook_entity_extra_field_info to register the extra fields. Normally it looks like

this:

```

function hook_entity_extra_field_info() {

  $extra_fields = [

    'entity_type' => [

return $extra_fields;

}

```

The class simply look like this:

```

<?php

namespace Drupal\your_module;

    return "String";

  }

}

```

The module needs both, the render_class key and the existing class defined

in the render_class key. The module only registers extra fields from type

"display" with the required key and the existing class. Views then

passes the entity to the static render function of the field.

-- FAQ --

## FAQ 

Q:  I register an extra field for node type "article". But views doesn't show

    me the extra field.