Resolve "Upgrade flutter framework"

Closes #29 (closed)

android/app/build.gradle

@@ -16,7 +16,7 @@ if (gradlePropertiesFile.exists()) {
 
 def flutterRoot = localProperties.getProperty('flutter.sdk')
 if (flutterRoot == null) {
-    throw new FileNotFoundException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
+    throw new GradleException("Flutter SDK not found. Define location with flutter.sdk in the local.properties file.")
 }
 
 def appVersionCode = gradleProperties.getProperty('app.versionCode')
@@ -41,14 +41,10 @@ if (keystorePropertiesFile.exists()) {
 android {
     compileSdkVersion 31
 
-    lintOptions {
-        disable 'InvalidPackage'
-    }
-
     defaultConfig {
         applicationId "org.benoitharrault.hangman"
-        minSdkVersion 21
-        targetSdkVersion 29
+        minSdkVersion 16
+        targetSdkVersion 30
         versionCode appVersionCode.toInteger()
         versionName appVersionName
         archivesBaseName = "$applicationId" + "_" + "$versionCode"