minor: update README for 4.12 release

Author: romani

README.md

@@ -18,6 +18,7 @@ This plugin provides coding rules from [Checkstyle](http://checkstyle.sourceforg
 
 Checkstyle Plugin|Sonar|Checkstyle|Jdk
 -----------------|-----|----------|---
+4.12|5.6.6|8.12|1.8
 4.11|5.6.6|8.11|1.8
 4.10.1|5.6.6|8.10.1|1.8
 4.10|5.6.6|8.10|1.8