FIX: Adds test case for escape_xml function

xlsx/src/export/test/test_escape.rs

@@ -16,10 +16,9 @@ fn test_escape_xml() {
         escape_xml("This is <>&\"' say"),
         "This is &lt;&gt;&amp;&quot;&apos; say"
     );
-}
 
-// '&' => "&amp;"
+    assert_eq!(
-// '<' "&lt;")
+        escape_xml("One line\nanother line\n\r"),
-// '>' => "&gt;"
+        "One line&#xA;another line&#xA;&#xD;"
-// '"' => "&quot;"
+    );
-// '\'' => "&apos;"
+}