docs: add intro of starting verstion

Author: aspirantzhang

README.md

@@ -19,6 +19,8 @@ You can use it to avoid wasting time typing Class blocks, function signatures or
 ## Special Thanks
 This extension is forked from [h4kst3r/php-awesome-snippets](https://github.com/h4kst3r/php-awesome-snippets). Because its author seems to have not maintained it for a long time. So I made this fork to make the extension suitable for new version of PHP. I re-planned the shortcut keys, and add more standardized writing methods. Great thanks to h4kst3r's excellent work.
 
+The new version number starts from 2.x.
+
 This work is inspired by PHPstorm (*PHP Live Templates*) and other works available on VScode marketplace like [PHP Snippets VS Code](https://github.com/heberalmeida/php-snippets) or [PHP Snippet Pack](https://github.com/jm-mwi/vscode-php-snippets/).
 
 ## License