📝 Readme update poa fullpage (#260)

* PoA - FullPage Support

* PoA CLI limitation

README.md

@@ -172,6 +172,7 @@ public class Example {
 - `driver` (**required**) - A selenium driver instance
 - `name` (**required**) - The screenshot name; must be unique to each screenshot
 - `options` (**optional**) - There are various options supported by percy.screenshot to server further functionality.
+  - `fullPage` - Boolean value by default it falls back to `false`, Takes full page screenshot [From CLI v1.27.6+]
   - `freezeAnimatedImage` - Boolean value by default it falls back to `false`, you can pass `true` and percy will freeze image based animations.
   - `freezeImageBySelectors` - List of selectors. Images will be freezed which are passed using selectors. For this to work `freezeAnimatedImage` must be set to true.
   - `freezeImageByXpaths` - List of xpaths. Images will be freezed which are passed using xpaths. For this to work `freezeAnimatedImage` must be set to true.