Docs: Add link to UI Tests

Author: shiki

docs/README.md

@@ -6,6 +6,7 @@
 - [Using Android Resources](using-android-resources.md) - describes how to add or use Android resources like strings and drawables
 - [Pull Request Guidelines](pull-request-guidelines.md) - branch naming and how to write good pull requests
 - [Subtree'd Library Projects](subtreed-library-projects.md) - how to deal with subtree dependencies
+- [UI Tests](../WordPress/src/androidTest/java/org/wordpress/android/e2e/)
 
 ## Accessibility