[Feat]: Full screen screenshot

Is your feature request related to a problem? Please describe.

Appium provides the option to either capture the screenshot of viewport or of the specific element on mobile screen. For screens, which require scroll in particular direction to load the remaining portion of content cannot be captured with the current methods available in Appium.

Describe the solution you'd like Appium UiAutomator2 and XCUITest driver already provides execute commands for gestures: https://github.com/appium/appium-uiautomator2-driver/blob/master/docs/android-mobile-gestures.md#mobile-scrollgesture https://appium.github.io/appium-xcuitest-driver/7.24/reference/execute-methods/#mobile-swipe https://appium.github.io/appium-xcuitest-driver/7.24/reference/execute-methods/#mobile-scroll

Perhaps we can make use of these gestures and provide a direction to scroll in and continue scrolling until the page source has not changed after scrolling meaning we have reached at the end of screen.

For each scroll, AppiumDriver should keep on capturing the screenshot of visible portion of screen, and then append the newly loaded portion of screen to existing screenshot to extend it and keep on doing it until scroll has reacched to the full length of screen.

Alternatively for every scroll, it can capture screenshot of visible portion, and then at the very end, it can merge all these screenshots from the first one to the last one excluding the common pixels of the consecutive screenshots so that there is no overlap of screenshot when merging two images.

Describe alternatives you've considered For web, I checked some third party libraries like ashot provide a way to take screenshot of full page, I have not been able to find a way to capture the full page screenshot for native mobile app screens.

Additional context This would is especially useful for performing image comparison and visual testing of mobile screens.