Add FAIR Pattern Importer plugin

[costdev]

This adds a WP-CLI command for importing patterns from JSON files.

Commands:

wp fair_patterns create_categories # Create the pattern categories, if missing, from a hardcoded list.
wp fair_patterns create_keywords # Create the pattern categories, if missing, from a hardcoded list.
wp fair_patterns import <dir> # Import patterns from a directory of JSON files.

For example:

• Ensure the Pattern Directory plugin is installed and activated.
• Get patterns from this endpoint
  • Change page until out of pages.
  • Save each set of results to a JSON file in a /path/to/patterns directory.
• Run wp fair_patterns create_categories to create the pattern categories.
• Run wp fair_patterns create_keywords to create the pattern keywords.
• Run wp fair_patterns import /path/to/patterns to import the patterns.