Apply PR from Vydia#320

Author: Greenheart

android/build.gradle

@@ -1,6 +1,11 @@
 buildscript {
+    // Simple helper that allows the root project to override versions declared by this library.
+    ext.safeExtGet = { prop, fallback ->
+        rootProject.ext.has(prop) ? rootProject.ext.get(prop) : fallback
+    }
+
     ext {
-        kotlinVersion = '1.7.20'
+        kotlinVersion = safeExtGet('kotlinVersion', '1.7.20')
         buildToolsVersion = '29.0.2'
         compileSdkVersion = 29
         targetSdkVersion = 29
@@ -25,10 +30,6 @@ def DEFAULT_COMPILE_SDK_VERSION = 28
 def DEFAULT_BUILD_TOOLS_VERSION = "28.0.3"
 def DEFAULT_TARGET_SDK_VERSION = 28
 
-def safeExtGet(prop, fallback) {
-    rootProject.ext.has(prop) ? rootProject.ext.get(prop) : fallback
-}
-
 android {
     compileSdkVersion safeExtGet('compileSdkVersion', DEFAULT_COMPILE_SDK_VERSION)
     buildToolsVersion safeExtGet('buildToolsVersion', DEFAULT_BUILD_TOOLS_VERSION)