web.xml

Você deve incluir o web.xml dentro da pasta WEB-INF juntamente com beans.xml e faces-config.xml:

Segue o meu:

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
        xmlns="http://java.sun.com/xml/ns/javaee" 
        xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" 
        id="WebApp_ID" version="3.0">

    <listener>
        <listener-class>org.apache.shiro.web.env.EnvironmentLoaderListener</listener-class>
    </listener>

    <filter>
        <filter-name>ShiroFilter</filter-name>
        <filter-class>org.apache.shiro.web.servlet.ShiroFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>ShiroFilter</filter-name>
        <url-pattern>/*</url-pattern>
        <dispatcher>REQUEST</dispatcher>
        <dispatcher>FORWARD</dispatcher>
        <dispatcher>INCLUDE</dispatcher>
        <dispatcher>ERROR</dispatcher>
    </filter-mapping>
</web-app>

Adicione isso no seu web.xml:

  <servlet-mapping>
    <servlet-name>Faces Servlet</servlet-name>
    <url-pattern>*.xhtml</url-pattern>
  </servlet-mapping>