Update android_uiautomator.md (#564)

Author: KazuCocoa

docs/android_uiautomator.md

@@ -5,3 +5,13 @@
     - [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
+
+# uiautomator2
+## difference between uiautomator1 and uiautomator2
+- `find_element/s :id, "ids"`
+    - uiautomator1
+        - Find elements with `resource_id`
+        - Find elements with string id resource(string.xml based)
+    - uiautomator2
+        - Find elements with `resource_id`
+    - from: Does not appium-uiautomator2-server support finding string ids with "id" strategy? [issue](https://github.com/appium/appium/issues/8349)