Make application/json5 a subclass of application/ecmascript

application/json used to inherit from application/ecmascript because it inherited from text/javascript which was incorrectly declared as a subclass of application/ecmascript. After the relationship between text/javascript and application/ecmascript was corrected (and application/json was made to inherit from the new application/json5 type instead), application/json's relationship to application/ecmascript was accidentally broken.