add xml shebang on top of xml file

src/telecaster/Clients/CosmohomeClient.py

@@ -260,7 +260,7 @@ def generate_xml():
     )
     xml_string = xml.decode('utf-8')
     final_xml = (
-        ''
+        '<?xml version="1.0" ?>'
         '<store name="cosmohome.gr" url="https://cosmohome.gr" encoding="utf8">'
         f'<date>{datetime.now().strftime("%Y-%m-%d %H:%M")}</date>'
         f"{xml_string}"