Add rule for operator spacing

[MAILPOET-2090]

tasks/code_sniffer/MailPoet/ruleset.xml

@@ -28,6 +28,11 @@
 
   <!-- Only short array syntax is allowed -->
   <rule ref="Generic.Arrays.DisallowLongArraySyntax"/>
+  <rule ref="Squiz.WhiteSpace.OperatorSpacing">
+    <properties>
+      <property name="ignoreNewlines" value="true" />
+    </properties>
+  </rule>
   <!-- Disallow usage of BOMs -->
   <rule ref="Generic.Files.ByteOrderMark"/>
   <!-- Lines can be 80 chars long, show errors at 120 chars -->