add_dictionary feils with Invalid DXF attribute "hande" for entity DICTIONARY

[gyanev]

Describe the bug

When calling add_dictionary for a new extension dictionaly of any graphical element:

pl = modelspace.add_polyline2d(polyline,  dxfattribs={'layer':line_layer})
xdict = pl.new_extension_dict()
adict = xdict.add_dictionary("adictname")

the following exception is trown:

  File "/home/yanev/projects/pd/pd-flow/.venv/lib/python3.8/site-packages/ezdxf/entities/xdict.py", line 191, in add_dictionary
    owner=dictionary.dxf.hande,
  File "/home/yanev/projects/pd/pd-flow/.venv/lib/python3.8/site-packages/ezdxf/entities/dxfns.py", line 134, in __getattr__
    raise const.DXFAttributeError(
ezdxf.lldxf.const.DXFAttributeError: Invalid DXF attribute "hande" for entity DICTIONARY

To Reproduce
Just call add_dictionary of extension dictionary.

Expected behavior
A dictionary object should be successfully created and returned.

[gyanev]

Actually while describing the issue I just realized that this is just a typo in ezdxf/entities/xdict.py in add_dictionary function. Line 191
owner=dictionary.dxf.hande,
should be
owner=dictionary.dxf.handle,

I just tested this change locally and it works fine.