Add `type` in composer JSON file

[ernilambar]

Example:

"type": "wordpress-plugin",

[raftaar1191]

The "type": "wordpress-plugin" field is already present in composer.json — it has been there since the very first commit (e5ac1401 on December 13, 2022, "add composer files"):

{
    "name": "wordpress/plugin-check",
    "description": "WordPress Plugin Check Plugin",
    "type": "wordpress-plugin",
    ...
}

This issue can be closed as it is already resolved.