Replace README.txt with README.md

ravi kant → made their first commit to this issue’s fork.

Updated readme file according README Templage.

Hi

I applied MR !1 and confirmed that it creates README.md file according to Drupal's template and standards.

For convenience below is the README.md content that the MR !1 created.

# CKEditor Tabber

This module adds a new button to Drupal 8 built-in CKEditor which allows the
user to create tabbed content on their pages.

The styling is very minimal, allowing the developers to overwrite the look
easily using CSS.

For a full description of the module, visit the
[project page](https://www.drupal.org/project/ckeditor_tabber).

Submit bug reports and feature suggestions, or track changes in the
[issue queue](https://www.drupal.org/project/issues/ckeditor_tabber).


## Table of contents

- Requirements
- Installation
- Configuration
- Maintainers


## Requirements

This module requires no modules outside of Drupal core.


## Installation

Install as you would normally install a contributed Drupal module. For further
information, see
[Installing Drupal Modules](https://www.drupal.org/docs/extending-drupal/installing-drupal-modules).


## Configuration

1. Go to Administration » Configuration » Content authoring » Text formats
   and editors
1. Edit a text format, for example "Basic HTML"
1. Drag and Drop the Add Tab button to the toolbar to show it to the users
1. Scroll down to the bottom to "Allowed HTML tags"
1. Find and replace `<dl>` with `<dl class>`
1. This makes sure CKEditor doesn't remove the class name Tabber uses

### Code structure example

```html
<section class="ckeditor-tabber-tabs"
  <ul class="tabs-holder">
    <li><a class="tab tab-1 active">Tab 1</a></li>
    <li><a class="tab tab-2">Tab 1</a></li>
  </ul>
  <div class="tabs-content-holder">
    <div class="tab-content tab-content-1 active">
      <p>Tab 1 contents</p>
    </div>
    <div class="tab-content tab-content-2">
      <p>Tab 2 contents</p>
    </div>
  </div>
</section>
```

## Maintainers

- Juhani Väätäjä - [j-vee](https://www.drupal.org/u/j-vee)
- Sébastien Corbin - [sebcorbin](https://www.drupal.org/u/sebcorbin)