Add Maven wrapper.

Change-Id: If2fa52c38df7434e6677d5aba09b564ad548541a
diff --git a/.mvn/wrapper/maven-wrapper.properties b/.mvn/wrapper/maven-wrapper.properties
new file mode 100644
index 0000000..642d572
--- /dev/null
+++ b/.mvn/wrapper/maven-wrapper.properties
@@ -0,0 +1,2 @@
+distributionUrl=https://repo.maven.apache.org/maven2/org/apache/maven/apache-maven/3.6.3/apache-maven-3.6.3-bin.zip
+wrapperUrl=https://repo.maven.apache.org/maven2/io/takari/maven-wrapper/0.5.6/maven-wrapper-0.5.6.jar