feature/display-first-channel

[evamaxfield]

Pull request recommendations:

• Name your pull request your-development-type/short-description. Ex: feature/read-tiff-files
• Link to any relevant issue in the PR description. Ex: Resolves [admin/build-py39 #12], adds tiff file format support

Resolves #2, always display something on initial load.

• Provide context of changes.

Balancing heavy initial load and immediate feedback to user, this will make it so that the first channel of an image will be rendered rather than nothing being rendered on initial load of the image.

Additionally, it upgrades the package to using the newly released napari_plugin_engine

• Provide relevant tests for your feature or bug fix.
• Provide or update documentation for any feature added by your pull request.

Thanks for contributing!

[tlambert03]

i think this should all work!