use utf-8 character encoding on static content

web.xml

<?xml version="1.0" encoding="utf8"?>
<!DOCTYPE web-app
PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
"http://java.sun.com/dtd/web-app_2_3.dtd">
<web-app>
  ...
  <mime-mapping>
    <extension>html</extension>
    <mime-type>text/html; charset=utf-8</mime-type>
  </mime-mapping>
  <mime-mapping>
    <extension>css</extension>
    <mime-type>text/css; charset=utf-8</mime-type>
  </mime-mapping>
  <mime-mapping>
    <extension>js</extension>
    <mime-type>text/javascript; charset=utf-8</mime-type>
  </mime-mapping>
</web-app>