docs: switch to main [ci skip][skip ci]

Author: adhocore

README.md

@@ -1,9 +1,9 @@
 ## adhocore/json-comment
 
 [![Latest Version](https://img.shields.io/github/release/adhocore/php-json-comment.svg?style=flat-square)](https://github.com/adhocore/php-json-comment/releases)
-[![Travis Build](https://img.shields.io/travis/adhocore/php-json-comment/master.svg?style=flat-square)](https://travis-ci.org/adhocore/php-json-comment?branch=master)
-[![Scrutinizer CI](https://img.shields.io/scrutinizer/g/adhocore/php-json-comment.svg?style=flat-square)](https://scrutinizer-ci.com/g/adhocore/php-json-comment/?branch=master)
-[![Codecov branch](https://img.shields.io/codecov/c/github/adhocore/php-json-comment/master.svg?style=flat-square)](https://codecov.io/gh/adhocore/php-json-comment)
+[![Travis Build](https://img.shields.io/travis/adhocore/php-json-comment/main.svg?style=flat-square)](https://travis-ci.org/adhocore/php-json-comment?branch=main)
+[![Scrutinizer CI](https://img.shields.io/scrutinizer/g/adhocore/php-json-comment.svg?style=flat-square)](https://scrutinizer-ci.com/g/adhocore/php-json-comment/?branch=main)
+[![Codecov branch](https://img.shields.io/codecov/c/github/adhocore/php-json-comment/main.svg?style=flat-square)](https://codecov.io/gh/adhocore/php-json-comment)
 [![StyleCI](https://styleci.io/repos/100117199/shield)](https://styleci.io/repos/100117199)
 [![Software License](https://img.shields.io/badge/license-MIT-brightgreen.svg?style=flat-square)](LICENSE)