protected DataTypeComponent addComponent(Structure es, DataType dt, String componentName) {
		return es.add(dt, dt.getLength(), componentName, null);
	}
Set the category of this data type.  

@param struct
@param buf
@return Returns a new structure with the correct category.
Ghidra/Framework/SoftwareModeling/src/main/java/ghidra/program/model/data/FactoryStructureDataType.java