A novel synthetised sulphonylhydrazone coumarin (E)‐4‐methyl‐N′‐(1‐(3‐oxo‐3H‐benzo[f]chromen‐2‐ yl)ethylidene)benzenesulphonohydrazide protect against isoproterenol‐induced myocardial infarction in rats by attenuating oxidative damage, biological changes and electrocardiogram