Add working tap command

Add TOUCH_SINGLE_TAP command with correct value according to JSON Wire Protocol.

Author: vs-dev-bg

src/main/java/io/appium/java_client/MobileCommand.java

@@ -34,6 +34,7 @@ public interface MobileCommand {
  String PULL_FOLDER = "pullFolder";
  String HIDE_KEYBOARD = "hideKeyboard";
  String RUN_APP_IN_BACKGROUND = "runAppInBackground";
+ String TOUCH_SINGLE_TAP = "touchSingleTap";
  String PERFORM_TOUCH_ACTION = "performTouchAction";
  String PERFORM_MULTI_TOUCH = "performMultiTouch";
  String IS_APP_INSTALLED = "isAppInstalled";