Instructions to upgrade to Cordova plugin version to 8.0

This chapter describes the steps to take in order to migrate Cordova plugin to 8.0

SecureXhr

If you are uing secureXhr flag and XMLHttpRequest api please update load and error handlers. Cordova Plugin from now on will correctly map the 400+ error codes as load events instead of error events. error events will still be called when the request was not sent.