UPDATE: Dump of initial files

xlsx/src/export/xml_constants.rs

@@ -0,0 +1,5 @@
+pub(crate) const XML_DECLARATION: &str =
+    r#"<?xml version="1.0" encoding="UTF-8" standalone="yes"?>"#;
+
+pub(crate) const XML_WORKSHEET: &str =
+    r#"http://schemas.openxmlformats.org/officeDocument/2006/relationships/worksheet"#;