Update example to follow current conventions. (#212)

Author: anuraaga

example/build.gradle

@@ -0,0 +1,13 @@
+plugins {
+  id("otel.java-conventions")
+}
+
+description = "An example OpenTelemetry Java Contrib library"
+
+tasks {
+  jar {
+    manifest {
+      attributes["Main-Class"] = "io.opentelemetry.contrib.example.Library"
+    }
+  }
+}

example/build.gradle.kts

@@ -0,0 +1,19 @@
+/*
+ * Copyright The OpenTelemetry Authors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package io.opentelemetry.contrib.example;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+import org.junit.jupiter.api.Test;
+
+class LibraryTest {
+
+  @Test
+  void myMethod() {
+    Library library = new Library();
+    assertThat(library.myMethod()).isTrue();
+  }
+}