Add <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> to root pom

pom.xml

@@ -12,6 +12,7 @@
   <url>https://github.com/Microsoft/botbuilder-java</url>
   
   <properties>
+    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <maven.deploy.skip>true</maven.deploy.skip>
   </properties>