Ruleset: selectively exclude an errorcode

As of PHPCS 4.0, it is possible to selectively exclude errors from the `PSR12.Files.FileHeader` sniff.

This particular exclusion means that we will not enforce a blank line between the PHP open tag and the file docblock, as that would cause a lot of unnecessary code churn in the primary codebases using this ruleset.

Author: jrfnl

PHPCSDev/ruleset.xml

@@ -49,6 +49,9 @@
              most external standards, adding constant visibility is not (yet) an option. -->
         <exclude name="PSR12.Properties.ConstantVisibility"/>
 
+        <!-- Allow for file docblock on the line directly following the PHP open tag. -->
+        <exclude name="PSR12.Files.FileHeader.SpacingAfterTagBlock"/>
+
         <!-- Allow for the first condition of a multi-line control structure to be on the same line
              as the control structure keyword. -->
         <exclude name="PSR12.ControlStructures.ControlStructureSpacing.FirstExpressionLine"/>