Split whitespace sniffers introduced in php/docbook-cs#35

Author: jordikroon

docbookcs.xml

@@ -13,7 +13,8 @@
   <sniff class="DocbookCS\Sniff\SimparaSniff" />
   <sniff class="DocbookCS\Sniff\ExceptionNameSniff" />
   <sniff class="DocbookCS\Sniff\AttributeOrderSniff" />
-  <sniff class="DocbookCS\Sniff\WhitespaceSniff" />
+  <sniff class="DocbookCS\Sniff\MixedIndentationSniff" />
+  <sniff class="DocbookCS\Sniff\TrailingWhitespaceSniff" />
  </sniffs>
 
  <paths>