Merge pull request #201 from mikehardy/allow-version-overrides

fix: use react-native convention for version overrides, allows AndroidX to work

Author: sumedht

android/build.gradle

@@ -2,13 +2,17 @@ apply plugin: 'com.android.library'
 repositories {
     mavenCentral()
 }
+def safeExtGet(prop, fallback) {
+    rootProject.ext.has(prop) ? rootProject.ext.get(prop) : fallback
+}
+
 android {
-    compileSdkVersion 26
-    buildToolsVersion "26.0.3"
+    compileSdkVersion safeExtGet('compileSdkVersion', 28)
+
 
     defaultConfig {
-        minSdkVersion 16
-        targetSdkVersion 26
+        minSdkVersion safeExtGet('minSdkVersion', 16)
+        targetSdkVersion safeExtGet('targetSdkVersion', 28)
         versionCode 1
         versionName "1.0"
     }