Add: WP-CLI command to bulk classify images

[dinhtungdu]

Description of the Change

Add a new WP CLI command image to (bulk) classify uploaded images. By default, this command classifies all images that don't have alt.

Arguments:

• attachment_ids: Comma delimeted Attachment IDs to classify

Flags:

• --limit=number: Limit classification to N attachments. Default false.
• --force: Force classification to first N attachments. Default false.

Alternate Designs

n/a.

Benefits

Able to classify images in bulk by using CLI.

Possible Drawbacks

n/a

Verification Process

Try possible options/flags above.

Checklist:

• I have read the CONTRIBUTING document.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests passed.

Applicable Issues

Closes #95

[ryanwelcher]

@dinhtungdu I think this is a nice approach. Well done!