Issue #3315710: Offline functionality of Anu LMS

The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),

and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

## Unreleased changes

- Get rid of "flatMap" in js code to provide better compatibility with old browsers.

## [2.9.0]

- #3312107: Highlighting should be applied for whole words.

- Improved global styles: set box-sizing and reflecting icons for RTL languages.

Drupal module which adds E-Learning capabilities with knowledge assessment tools.

## Compatible

Anu LMS supports the following platforms:

### Desktop Platforms:

- Firefox 53+

- Chrome 49+

- Opera 36+

- Edge 80+

### Mobile Platforms:

- iOS (Chrome, Safari) v14.4+

- Android (Chrome, Firefox) 7+

## How is to configure PWA?

PWA means "Progressive web app". After installing [pwa](https://www.drupal.org/project/pwa) module, Anu LMS will be able to "make course available offline" without access to internet on a user's device.

To enable offline courses just install and configure "pwa" module. Configurations by default work well with Anu LMS. If you want to customize any PWA property - go to `/admin/config/pwa/settings` page.

## Development

### Installation

1. Install a clean Drupal 9 site ([Instructions for DDEV](https://ddev.readthedocs.io/en/latest/users/cli-usage/#drupal-9-quickstart)).

2. Prepare composer for Anu LMS installation:

  ```

  composer config minimum-stability dev

  composer config repositories.anu vcs git@github.com:systemseed/anu_lms.git

  composer req  --prefer-source systemseed/anu_lms:"2.x-dev"

  composer require 'drupal/anu_lms:^2.9'

  ```

3. Enable Anu LMS module and the demo content

```

Demo courses page will be available at /anu-demo after module installation.

All demo content is deleted on module uninstall.

## TODO List

### Beta release:

* Add path alias patterns https://github.com/systemseed/anu_lms/issues/160

* Provide documentation for recommended permission configuration after module's installation

* Add a validation for quiz content creating experience. I.e. do not allow multiple options for single option response.

* Add normal UI for errors handling on quizzes instead of ugly alert().

* Disable access to lessons when course is not in the group

* Add basic automated tests coverage https://github.com/systemseed/anu_lms/issues/157

### Full release

* https://github.com/systemseed/anu_lms/issues/161

* Disabled Slider has small balloon offset

* Create default courses page https://github.com/systemseed/anu_lms/issues/158

* Create a style guide

* Documentation

* Integration with [Drupal.org](https://www.drupal.org/project/anu_lms)

### To discuss

* Potential issue with display of quiz scoring after the amount of quiz questions has changed (You scored X out of Y).

* Get rid of Features dependency - we may let developers decide how they want to get ANU LMS updates

* Get rid of Rest Entity Recursive dependency for better performance