Update Appium tests readme.md (#16134)

* Update readme.md

* Update readme.md

---------

Co-authored-by: Jumar Macato <[email protected]>

Author: maxkatz6

tests/Avalonia.IntegrationTests.Appium/readme.md

@@ -27,4 +27,11 @@
 
 Each time you make a change to Avalonia or `IntegrationTestApp`, re-run the `bundle.sh` script (registration only needs to be done once).
 
-
+### Appium 2
+
+Tests in this project are configured to run with Appium 1 (as only this version supports WinAppDriver).
+If you need to run with Appium 2 on macOS, extra steps are required:
+- Install Appium 2 with [mac2 driver](https://github.com/appium/appium-mac2-driver)
+- Set `<IsRunningAppium2>true</IsRunningAppium2>` msbuild property on the test project or globally
+- Run appium 2 with `appium --base-path=/wd/hub` (custom base path is required)
+- Run tests as normally