metadata.json has the wrong type property value

[costdev]

The spec for the type property for Metadata Documents states:

This property MUST be a valid string. The property SHOULD use a type defined in the type registry.

While "SHOULD" is not "MUST", the type registry shows that WordPress plugins and themes already have defined respective types of wp-plugin and wp-theme.

The metadata.json file shows:

{
  "type": "plugin"
}

This should be:

{
  "type": "wp-plugin"
}