fix: Remove duplicate dataclass attributes when they have defaults

Fixes #52

Author: bstadlbauer

src/pytkdocs/objects.py

@@ -255,6 +255,14 @@ def add_child(self, obj: "Object") -> None:  # noqa: WPS231 (not complex)
         elif isinstance(obj, Method):
             self.methods.append(obj)  # type: ignore
         elif isinstance(obj, Attribute):
+            # Dataclass attributes with default values will already be present in `self.attributes` as they are
+            # resolved differently by the python interpreter. Aas they have a concrete value, they are already present
+            # in the "original" class. They should be overridden with the new "dataclass" attribute coming in here
+            # (having the "dataclass_field" property set)
+            new_attribute_name = obj.name
+            for attribute in self.attributes:
+                if attribute.name == new_attribute_name:
+                    self.attributes.remove(attribute)
             self.attributes.append(obj)  # type: ignore
         obj.parent = self