Update Gradle 8 compatibility

android/build.gradle

@@ -2,14 +2,14 @@ group 'boi.walle.modal_progress_hud_nsn'
 version '0.4.0'
 
 buildscript {
-    ext.kotlin_version = '1.7.10'
+    ext.kotlin_version = '1.9.20'
     repositories {
         google()
         mavenCentral()
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:7.2.0'
+        classpath 'com.android.tools.build:gradle:8.1.4'
         classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
     }
 }
@@ -25,7 +25,11 @@ apply plugin: 'com.android.library'
 apply plugin: 'kotlin-android'
 
 android {
-    compileSdkVersion 31
+    if (project.android.hasProperty("namespace")) {
+        namespace 'boi.walle.modal_progress_hud_nsn'
+    }
+
+    compileSdk 31
 
     compileOptions {
         sourceCompatibility JavaVersion.VERSION_1_8