docs: update README with simple usage and updates

README.md

@@ -2,7 +2,7 @@
 
 [![Latest Version](https://img.shields.io/github/release/hussainweb/date-converter.svg?style=flat-square)](https://github.com/hussainweb/date-converter/releases)
 [![Software License](https://img.shields.io/badge/license-GPLv2-brightgreen.svg?style=flat-square)](LICENSE)
-[![Build Status](https://img.shields.io/travis/hussainweb/date-converter/master.svg?style=flat-square)](https://travis-ci.org/hussainweb/date-converter)
+[![Build Status](https://img.shields.io/github/workflow/status/hussainweb/date-converter/PHP%20tests%20and%20style%20checks?style=flat-square)](https://github.com/hussainweb/date-converter/actions/workflows/test.yml)
 [![Total Downloads](https://img.shields.io/packagist/dt/hussainweb/date-converter.svg?style=flat-square)](https://packagist.org/packages/hussainweb/date-converter)
 
 Date Converter is a PHP library to convert dates across various calendars. Currently, support for only various Hijri calendars is planned.
@@ -11,6 +11,15 @@ Date Converter is a PHP library to convert dates across various calendars. Curre
 
 Via Composer
 
-``` bash
-$ composer require hussainweb/date-converter
+```bash
+composer require hussainweb/date-converter
+```
+
+## Usage
+
+To convert between dates, use the respective `Algorithm` class. Similar to [PHP's in-built date conversion functions](https://www.php.net/manual/en/function.gregoriantojd.php), these classes work with Julian Day as a primary means to convert dates.
+
+```php
+$algorithm = new HijriFatimidAstronomical();
+$hijri_date = $algorithm->fromJulianDay(2457198); // 8-9-1436
 ```