docs: Initiate Selenium client compatibility matrix

Author: valfirst

README.md

@@ -87,7 +87,15 @@ dependencies {
 }
 ```
 
-### How to pin Selenium dependencies?
+### Compatibility Matrix
+| Appium Java Client | Selenium client                             |
+|--------------------|---------------------------------------------|
+| `8.5.0`            | `4.9.1`                                     |
+| `8.4.0`            | `4.8.2`, `4.8.3`, `4.9.0`                   |
+| `8.3.0`            | `4.7.0`, `4.7.1`, `4.7.2`, `4.8.0`, `4.8.1` |
+| `8.2.1`            | `4.5.0`, `4.5.1`, `4.5.2`, `4.5.3`, `4.6.0` |
+
+#### How to pin Selenium dependencies?
 
 Appium Java Client declares Selenium dependencies using open version range which is handled in differently by different
 build tools. Sometimes users may want to pin used Selenium dependencies for [various reasons](https://github.com/appium/java-client/issues/1823).
@@ -242,4 +250,4 @@ Visit [CHANGELOG.md](CHANGELOG.md) to see the full list of changes between versi
 
 Run a test using
 
->  gradle clean -Dtest.single=IOSAlertTest test
+>  gradle clean -Dtest.single=IOSAlertTest test