Add support for PHP 8.1 and remove support for PHP 7.3

.travis.yml

@@ -1,9 +1,9 @@
 language: php
 
 php:
-  - 7.3
   - 7.4
   - 8.0
+  - 8.1
 
 before_install:
   - composer self-update

README.md

@@ -1,7 +1,7 @@
 # language-detection
-| Build Status | Code Coverage | Version | Total Downloads | Minimum PHP Version | License |
-| :---: | :---: | :---: | :---: | :---: | :---: |
-| [![Build Status](https://travis-ci.org/patrickschur/language-detection.svg?branch=master)](https://travis-ci.org/patrickschur/language-detection) | [![codecov](https://codecov.io/gh/patrickschur/language-detection/branch/master/graph/badge.svg)](https://codecov.io/gh/patrickschur/language-detection) | [![Version](https://img.shields.io/packagist/v/patrickschur/language-detection.svg?style=flat-square)](https://packagist.org/packages/patrickschur/language-detection) | [![Total Downloads](https://img.shields.io/packagist/dt/patrickschur/language-detection.svg?style=flat-square)](https://packagist.org/packages/patrickschur/language-detection) | [![Minimum PHP Version](https://img.shields.io/badge/php-%3E%3D%207.3-4AC51C.svg?style=flat-square)](https://php.net/) | [![License](https://img.shields.io/packagist/l/patrickschur/language-detection.svg?style=flat-square)](https://opensource.org/licenses/MIT) |
+| Build Status | Code Coverage | Version | Total Downloads |                                                  Minimum PHP Version                                                   | License |
+| :---: | :---: | :---: | :---: |:----------------------------------------------------------------------------------------------------------------------:| :---: |
+| [![Build Status](https://travis-ci.org/patrickschur/language-detection.svg?branch=master)](https://travis-ci.org/patrickschur/language-detection) | [![codecov](https://codecov.io/gh/patrickschur/language-detection/branch/master/graph/badge.svg)](https://codecov.io/gh/patrickschur/language-detection) | [![Version](https://img.shields.io/packagist/v/patrickschur/language-detection.svg?style=flat-square)](https://packagist.org/packages/patrickschur/language-detection) | [![Total Downloads](https://img.shields.io/packagist/dt/patrickschur/language-detection.svg?style=flat-square)](https://packagist.org/packages/patrickschur/language-detection) | [![Minimum PHP Version](https://img.shields.io/badge/php-%3E%3D%207.4-4AC51C.svg?style=flat-square)](https://php.net/) | [![License](https://img.shields.io/packagist/l/patrickschur/language-detection.svg?style=flat-square)](https://opensource.org/licenses/MIT) |
 
 This library can detect the language of a given text string.
 It can parse given training text in many different idioms into a sequence of [N-grams](https://en.wikipedia.org/wiki/N-gram) and builds a database file in PHP to be used in the detection phase.

composer.json

@@ -24,7 +24,7 @@
     }
   },
   "require": {
-    "php": "^7.3 || ^8.0",
+    "php": "^7.4 || ^8.0",
     "ext-mbstring": "*",
     "ext-json": "*"
   },