The method setAppendExisting(boolean) is undefined for the type ExtentHtmlReporter in v 4.0.0

[hrishikesh-shukla]

In version 3.1.2, we were using setAppendExisting method via ExtentHtmlReporter class as it was implementing ReportAppendable interface but in 4.0.0, ExtentHtmlReporter class is no more implementing the ReportAppendable interface which is causing compile time error when migrating from 3.1.2 to 4.0.0.