function onMention( mention ) {
			if ( mention.action === 'PR-URL' ) {
				out += ' [(#' + trim( mention.ref ) + ')](' + mention.url + ')';
			} else if ( RE_CO_AUTHORED_BY.test( mention.action ) ) {
				authors.push( replace( mention.ref, RE_EMAIL, '' ) );
			}
		}
Callback invoked upon encountering a mention.

@private
@param {Object} mention - mention object