fix: align kotlinVersion with react-native-gradle-plugin

The `kotlinVersion` ext property was set to 2.1.20 while the
react-native-gradle-plugin included build brings
kotlin-gradle-plugin 2.2.0 on the classpath. This mismatch causes
third-party libraries that read `rootProject.ext.kotlinVersion` to
resolve incompatible KSP versions, breaking Android builds.

Author: cortinico

template/android/build.gradle

@@ -5,7 +5,7 @@ buildscript {
         compileSdkVersion = 36
         targetSdkVersion = 36
         ndkVersion = "27.1.12297006"
-        kotlinVersion = "2.1.20"
+        kotlinVersion = "2.2.0"
     }
     repositories {
         google()