Update best practices

Add article discussing the importance of using the latest support PHP versions.

Author: brianleejackson

_posts/16-08-01-Sites.md

@@ -16,6 +16,7 @@ PHP versions
 
 * [PHP Best Practices](https://phpbestpractices.org/)
 * [Best practices for Modern PHP Development](https://www.airpair.com/php/posts/best-practices-for-modern-php-development)
+* [Why You Should Be Using Supported PHP Versions](https://kinsta.com/blog/php-versions/)
 
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