add doc for uiautomator (#508)

Author: KazuCocoa

docs/android_uiautomator.md

@@ -0,0 +1,7 @@
+# Help debugging
+
+- `adb shell uiautomator events` 
+    - Prints out accessibility events to the console until the connection to the device is terminated
+    - [URL](https://stuff.mit.edu/afs/sipb/project/android/docs/tools/help/uiautomator/index.html)
+    - **notice**
+        - If Appium is started then it terminates the other `uiautomator` processes