Update 'Object Type Definitions'

Object-Type-Definitions.md

@@ -25,6 +25,12 @@ Currently, object section syntax does not support nested object definitions.
 Each member should start with a permission, then have a name, then a type specifier. After that,
 they can have an optional initialization value.
 
+Arf supports bitfields, like in C, although it is done with an amperseand symbol. This is a member of type integer with a width of 1:
+
+```
+ro someMember:Int & 1
+```
+
 # Semantics
 
 The "type" of an object type definition is what object it inherits. Most objects