modernize example app

usbSerialExamples/build.gradle

@@ -4,6 +4,11 @@ android {
     compileSdkVersion 28
     buildToolsVersion '28.0.3'
 
+    compileOptions {
+        sourceCompatibility JavaVersion.VERSION_1_8
+        targetCompatibility JavaVersion.VERSION_1_8
+    }
+
     defaultConfig {
         minSdkVersion 17
         targetSdkVersion 28
@@ -21,4 +26,6 @@ android {
 
 dependencies {
     implementation project(':usbSerialForAndroid')
+    implementation 'androidx.appcompat:appcompat:1.1.0'
+    implementation 'com.google.android.material:material:1.1.0'
 }