Add required namespaces for recently added pom file

Author: vitali-pr

itext7core/pom.xml

@@ -1,5 +1,6 @@
-<project>
-  <modelVersion>4.0.0</modelVersion>
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+<modelVersion>4.0.0</modelVersion>
   <groupId>com.itextpdf</groupId>
   <artifactId>itext7-core</artifactId>
   <version>8.0.1-SNAPSHOT</version>