Added default factory to numpy color creation

[JoOkuma]

Hey @quantumjot ,

I was getting this error:

  File "C:\Users\jordao\Mamba\envs\tracking\Lib\site-packages\napari_arboretum\_hookimpls.py", line 1, in <module>
    from napari_arboretum.plugin import Arboretum
  File "C:\Users\jordao\Mamba\envs\tracking\Lib\site-packages\napari_arboretum\plugin.py", line 10, in <module>
    from napari_arboretum.io.svg import export_svg
  File "C:\Users\jordao\Mamba\envs\tracking\Lib\site-packages\napari_arboretum\io\svg.py", line 5, in <module>
    from napari_arboretum.tree import Annotation, Edge
  File "C:\Users\jordao\Mamba\envs\tracking\Lib\site-packages\napari_arboretum\tree.py", line 27, in <module>
    @dataclass
     ^^^^^^^^^
  File "C:\Users\jordao\Mamba\envs\tracking\Lib\dataclasses.py", line 1230, in dataclass
    return wrap(cls)
           ^^^^^^^^^
  File "C:\Users\jordao\Mamba\envs\tracking\Lib\dataclasses.py", line 1220, in wrap
    return _process_class(cls, init, repr, eq, order, unsafe_hash,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\jordao\Mamba\envs\tracking\Lib\dataclasses.py", line 958, in _process_class
    cls_fields.append(_get_field(cls, name, type, kw_only))
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "C:\Users\jordao\Mamba\envs\tracking\Lib\dataclasses.py", line 815, in _get_field
    raise ValueError(f'mutable default {type(f.default)} for field '
ValueError: mutable default <class 'numpy.ndarray'> for field color is not allowed: use default_factory

This PR fixes this issue.

[codecov-commenter]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (9b19b26) 87.00% compared to head (99aa19b) 87.00%.

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Additional details and impacted files

@@           Coverage Diff           @@
##             main     #106   +/-   ##
=======================================
  Coverage   87.00%   87.00%           
=======================================
  Files          11       11           
  Lines         554      554           
  Branches       80       84    +4     
=======================================
  Hits          482      482           
  Misses         63       63           
  Partials        9        9           

Files Changed	Coverage Δ
src/napari_arboretum/tree.py	86.48% <100.00%> (ø)

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[deprecated-napari-hub-preview-bot]

Preview page for your plugin is ready here:
https://preview.napari-hub.org/lowe-lab-ucl/arboretum/106
Updated: 2023-08-29T13:24:58.788107

[JoOkuma]

@quantumjot, I fixed the linting error.

[quantumjot]

Thanks @JoOkuma !