Add napari file reader plugin for coco and via bounding boxes annotation file

[manashk29]

Hi @sfmig
There is currently no napari plugin infrastructure in ethology.

Add a napari npe2 file reader plugin to ethology so that users
can drag and drop any COCO or VIA JSON annotation file directly
into the napari viewer.

reader will:

• Detects whether droped file is coco or via.
• Return 'None' for non annotation json files
• Converts ethology's internal center based bbox coordinates
  to napari's (col's, row's) corner coordinates.
• Display's all bbox as a shapes layer
  ( category_name , image_id , category_id )
• If files has no valid annotation then return empty layer with a warning
  so napari will not fall back.

This also creates the npe2 plugin infrastructure
'ethology/napari.yaml' , 'pyproject.toml' entry point that
all future users will use.

I am happy to implement this.