Formatter now accepts XMLs with prologs

Backend-libXML/Parser.py

@@ -7,8 +7,15 @@ def prettify(source: str) -> str:
     :param source: XML
     :return: prettified XML
     """
+    prolog = ""
+    prolog_start = source.find("<?")
+    
+    if prolog_start != -1:
+        prolog_end = source.find("?>") + 2
+        prolog = source[prolog_start:prolog_end] + "\n"
+        source = source[prolog_end: ]
     xml = etree.XML(source)
-    return etree.tostring(xml, pretty_print=True).decode()
+    return prolog + etree.tostring(xml, pretty_print=True).decode()
 
 def minimize(source: str) -> str:
     """Method used to minimize XML by deleting not needed whitespaces.