Update tested version of Firefox in readme. [ci skip]
Update tested version of Firefox in readme. [ci skip]

nonconforme/platform.js,Keystion/platform.js,bestiejs/platform.js,bestiejs/platform.js,am11/platform.js,nonconforme/platform.js,am11/platform.js,bestiejs/platform.js,am11/platform.js,nonconforme/platform.js,Keystion/platform.js,Keystion/platform.js