Fix privatePropertyPattern to contain underscores

Author: xenomachina

detekt.yml

@@ -319,7 +319,7 @@ naming:
     active: true
     constantPattern: '[A-Z][_A-Z0-9]*'
     propertyPattern: '[A-Za-z][_A-Za-z0-9]*'
-    privatePropertyPattern: '(_)?[A-Za-z][A-Za-z0-9]*'
+    privatePropertyPattern: '(_)?[A-Za-z][_A-Za-z0-9]*'
   VariableMaxLength:
     active: false
     maximumVariableNameLength: 64