po: add Zanata configuration

zanata.xml

+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+
+<!--
+	Maintainers:
+	do a "make -C po NetworkManager.pot" before "zanata-cli push"
+-->
+
+<config xmlns="http://zanata.org/namespace/config/">
+	<url>https://translate.zanata.org/</url>
+	<project>NetworkManager</project>
+	<project-version>master</project-version>
+	<project-type>gettext</project-type>
+	<src-dir>po</src-dir>
+	<trans-dir>po</trans-dir>
+	<rules/>
+</config>