Add disposable_nil rule

xcode/.swiftlint.yml

@@ -251,6 +251,12 @@ custom_rules:
     message: "The parameter name is actually used in the function name. Use _ instead."
     severity: error
 
+  disposable_nil:
+    name: "Disposable nil"
+    regex: ' *\S*(d|D)isposable *= *nil'
+    message: "Use `dispose()` instead of nil."
+    severity: error
+
   # Rx
 
   unused_map_parameter: